TWI638057B - Free cutting copper alloy and method for manufacturing the same (2) - Google Patents

Abstract

The invention provides a free-cutting copper alloy, which contains 75.0 to 78.5% Cu, 2.95 to 3.55% Si, 0.07 to 0.28% Sn, 0.06 to 0.14% P, and 0.022 to 0.25% Pb, and the remainder Including Zn and unavoidable impurities, the composition satisfies the following relationship: 76.2 f1 = Cu + 0.8 × Si-8.5 × Sn + P + 0.5 × Pb 80.3, 61.5 f2 = Cu-4.3 × Si-0.7 × Sn-P + 0.5 × Pb 63.3, the area ratio (%) of the constituent phases satisfies the following relationship: 25 kappa 65, 0 γ 1.5, 0 β 0.2, 0 μ 2.0, 97.0 f3 = α + κ, 99.4 f4 = α + κ + γ + μ, 0 f5 = γ + μ 2.5, 27 f6 = κ + 6 × γ1 / 2 + 0.5 × μ 70, and the long side of the γ phase is 40 μm or less, the long side of the μ phase is 25 μm or less, and the k phase is present in the α phase.

Description

Free-cutting copper alloy and manufacturing method of free-cutting copper alloy (2)

The invention relates to a method for manufacturing a free-cutting copper alloy and free-cutting copper alloy having excellent corrosion resistance, excellent impact characteristics, high strength, high-temperature strength, and a significant reduction in lead content. In particular, it is related to an appliance used in faucets, valves, joints and the like used in daily drinking water for humans and animals and valves, joints, and valves used in various harsh environments. Manufacturing method of machinable copper alloy and free-milling copper alloy.

This application claims priority based on Japanese Patent Application No. 2016-159238 filed in Japan on August 15, 2016, the contents of which are incorporated herein by reference.

Conventionally, copper alloys containing 56 ~ 65mass% Cu and 1 ~ 4mass% Pb have been used as copper alloys used in electrical / automotive / mechanical / industrial piping, including drinking water appliances. And the remaining part is made of Cu-Zn-Pb alloy (so-called free-cutting brass) of Zn or containing 80 ~ 88mass% of Cu, 2 ~ 8mass% of Sn, and 2 ~ 8mass% of Pb, and the remaining part is made of Zn Cu-Sn-Zn-Pb alloy (so-called bronze: gun copper).

However, in recent years, the impact of Pb on the human body and the environment has become worrying, and restrictions on Pb in various countries have become more active. For example, in California, the United States since January 2010, and in the United States since January 2014, restrictions on the Pb content in drinking water appliances and the like to be less than 0.25 mass% have come into effect. It is understood that the leaching amount of Pb to drinking water will be limited to about 5 mass ppm in the future. In countries other than the United States, its restriction movement has also developed rapidly, requiring the development of copper alloy materials that respond to the restrictions on Pb content.

In addition, in other industrial fields, automotive, mechanical, and electrical / electronic equipment fields, for example, the Pb content of free-cutting copper alloys in the European ELV and RoHS restrictions has reached 4 mass% except for the same as in the drinking water field. Active enhancements to Pb content including elimination of exceptions are being actively discussed.

The Pb-restriction enhancement trend of this free-cutting copper alloy advocates a copper alloy with a machinability function and containing Bi and Se, or a Cu and Zn alloy by increasing the β phase to improve the machinability and contain a high concentration Instead of Pb.

For example, Patent Document 1 proposes that if only Bi is contained instead of Pb, the corrosion resistance is insufficient. In order to reduce the β phase and isolate the β phase, the hot extruded rod after the hot extrusion is slowly cooled to 180 ° C and then heat treated. .

In Patent Document 2, 0.7 is added to the Cu-Zn-Bi alloy. ~ 2.5mass% of Sn to precipitate the γ phase of Cu-Zn-Sn alloy, thereby improving the corrosion resistance.

However, as shown in Patent Document 1, an alloy containing Bi instead of Pb has a problem in terms of corrosion resistance. In addition, Bi has many problems including the possibility that it is harmful to the human body in the same way as Pb, a problem in resources due to being a rare metal, and a problem that the copper alloy material becomes brittle. In addition, as proposed in Patent Documents 1 and 2, even if the β phase is isolated by slow cooling or heat treatment after hot extrusion to improve the corrosion resistance, the improvement of the corrosion resistance in a harsh environment cannot be achieved after all.

Further, as shown in Patent Document 2, even if the γ phase of a Cu-Zn-Sn alloy is precipitated, the γ phase inherently lacks corrosion resistance compared to the α phase, so that improvement in corrosion resistance under severe environments cannot be achieved after all. In addition, in the Cu-Zn-Sn alloy, the machinability of the γ phase containing Sn is so poor that it needs to be added together with Bi having machinability.

On the other hand, for copper alloys containing a high concentration of Zn, compared with Pb, the machinability of the β phase is poor, so not only cannot replace the free-cutting copper alloy containing Pb, but also corrosion resistance due to the inclusion of many β phases In particular, resistance to dezincification and stress corrosion cracking are very poor. In addition, since these copper alloys have low strength at high temperatures (for example, 150 ° C), they cannot cope with thin walls, such as automotive components used under hot sun and high temperatures near the engine room, and piping used under high temperature / high pressure. Light and lightweight.

In addition, Bi embrittles the copper alloy and expands if it contains many β phases. Due to its reduced properties, copper alloys containing Bi or copper alloys containing many β phases are not suitable as materials for automobiles, machinery, electrical components, and drinking water appliances including valves. Furthermore, brass containing Cu and Zn phase in the Cu-Zn alloy cannot improve stress corrosion cracking, has low strength at high temperatures, and has poor impact characteristics, and is therefore not suitable for use in these applications.

On the other hand, as a free-cutting copper alloy, for example, Patent Documents 3 to 9 propose a Cu-Zn-Si alloy containing Si instead of Pb.

In Patent Documents 3 and 4, those having mainly a machinability function having an excellent γ phase are used to achieve excellent machinability by not containing Pb or containing a small amount of Pb. By containing Sn in an amount of 0.3 mass% or more, the formation of a γ phase having a machinability function is increased and promoted, thereby improving machinability. Further, in Patent Documents 3 and 4, corrosion resistance is improved by forming many γ phases.

In Patent Document 5, it is assumed that a very small amount of Pb is contained in an amount of 0.02 mass% or less, and the total content area of the γ phase and the κ phase is mainly determined to obtain excellent machinability. Here, Sn acts to form and increase a γ phase, thereby improving erosion corrosion resistance.

In addition, in Patent Documents 6 and 7, casting products of Cu-Zn-Si alloys are proposed. In order to reduce the size of the casting grains, Zr contains a very small amount of Zr in the presence of P, and pays attention to the P / Zr ratio.

Further, Patent Document 8 proposes a copper alloy containing Fe in a Cu-Zn-Si alloy.

In addition, Patent Document 9 proposes that Cu-Zn-Si alloy contains Sn, Copper alloys of Fe, Co, Ni, Mn.

Here, as described in Patent Literature 10 and Non-Patent Literature 1, it is known that in the above-mentioned Cu-Zn-Si alloy, even if the composition is limited to a Cu concentration of 60 mass% or more, a Zn concentration of 30 mass% or less, and a Si concentration of Below 10mass%, in addition to the matrix α phase, there are 10 metal phases including β phase, γ phase, δ phase, ε phase, ζ phase, η phase, κ phase, μ phase, and χ phase. There are 13 kinds of metal phases including α ', β', and γ '. In addition, it is well known from experience that if an additional element is added, the metallographic structure becomes more complicated, and new phases and intermetallic compounds may appear. In addition, the alloy obtained from the equilibrium state diagram and the alloy actually produced are There is a large deviation in the composition of the existing metal phase. In addition, it is known that the composition of these phases also changes depending on the concentration of Cu, Zn, Si, etc. of the copper alloy and the thermal history of processing.

However, although the γ phase has excellent cutting performance, since the Si concentration is high and it is hard and brittle, if many γ phases are included, it will occur in corrosion resistance, impact characteristics, high temperature strength (high temperature creep), etc. under harsh environments. problem. Therefore, the use of a Cu-Zn-Si alloy containing a large amount of γ phases is also limited in the same way as a copper alloy containing Bi or a copper alloy containing many β phases.

Furthermore, the Cu-Zn-Si alloys described in Patent Documents 3 to 7 show relatively good results in the dezincification corrosion test based on ISO-6509. However, in the dezincification corrosion test based on ISO-6509, Whether the dezincification and corrosion resistance in the water was good or not, the copper chloride reagent, which was completely different from the actual water quality, was evaluated in a short time of only 24 hours. That is, the evaluation was performed in a short time using a reagent different from the actual environment, and therefore the corrosion resistance in a severe environment could not be fully evaluated.

In addition, Patent Document 8 proposes a case where Fe is contained in a Cu-Zn-Si alloy. However, Fe and Si form Fe-Si intermetallic compounds that are harder and more brittle than the γ phase. This intermetallic compound has problems such as shortening the life of a cutting tool during cutting processing, forming hard spots during polishing, and causing a problem in appearance. In addition, the additive element Si is consumed as an intermetallic compound, and the performance of the alloy is reduced.

In addition, in Patent Document 9, although Cu and Zn-Si alloy are added with Sn, Fe, Co, and Mn, Fe, Co, and Mn all combine with Si to form a hard and brittle intermetallic compound. Therefore, as in Patent Document 8, a problem occurs during cutting and grinding. In addition, according to Patent Document 9, a β phase is formed by containing Sn and Mn, but the β phase causes severe dezincification corrosion, thereby improving the susceptibility to stress corrosion cracking.

[Prior technical literature] (Patent Literature)

[Patent Document 1] Japanese Patent Laid-Open No. 2008-214760

[Patent Document 2] International Publication No. 2008/081947

[Patent Document 3] Japanese Patent Laid-Open No. 2000-119775

[Patent Document 4] Japanese Patent Laid-Open No. 2000-119774

[Patent Document 5] International Publication No. 2007/034571

[Patent Document 6] International Publication No. 2006/016442

[Patent Document 7] International Publication No. 2006/016624

[Patent Document 8] Japanese Patent Publication No. 2016-511792

[Patent Document 9] Japanese Patent Laid-Open No. 2004-263301

[Patent Document 10] US Patent No. 4,055,445

[Non-patent literature]

[Non-Patent Document 1]: Mima Genjiro and Hasegawa Masaharu: Prospects for Copper Technology Research, 2 (1963), P.62 ~ 77

The present invention has been made in order to solve such a prior art problem, and an object thereof is to provide a free-cutting copper alloy and a method for manufacturing a free-cutting copper alloy which are excellent in corrosion resistance, impact characteristics, and high-temperature strength under severe environments. In addition, in this specification, unless otherwise stated, corrosion resistance refers to both dezincification resistance and stress corrosion cracking resistance.

In order to solve this problem and achieve the aforementioned object, the free-cutting copper alloy according to the first aspect of the present invention is characterized by containing Cu (copper) of 75.0 mass% or more and 78.5 mass% or less, 2.95 mass% or more and 3.55 masses. % Si (silicon), 0.07 mass% to 0.28 mass% Sn (tin), 0.06 mass% to 0.14 mass% P (phosphorus), and 0.022 mass% to 0.25 mass% Pb ( Lead), and the remainder includes Zn (zinc) and unavoidable impurities. When the content of Cu is [Cu] mass%, the content of Si is [Si] mass%, and the content of Sn is [Sn ] mass%, the content of P is [P] mass%, and the content of Pb is [Pb] mass%, which has the following relationship: 76.2 f1 = [Cu] + 0.8 × [Si] -8.5 × [Sn] + [P] + 0.5 × [Pb] 80.3, 61.5 f2 = [Cu] -4.3 × [Si] -0.7 × [Sn]-[P] + 0.5 × [Pb] 63.3 In the constituent phases of the metallurgical structure, the area ratio of the α phase is (α)%, the area ratio of the β phase is (β)%, and the area ratio of the γ phase is (γ) )%, The area ratio of the κ phase is (κ)%, and the area ratio of the μ phase is (μ)%, which has the following relationship: 25 (κ) 65, 0 (γ) 1.5, 0 (β) 0.2, 0 (μ) 2.0, 97.0 f3 = (α) + (κ), 99.4 f4 = (α) + (κ) + (γ) + (μ), 0 f5 = (γ) + (μ) 2.5, 27 f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) The length of the long side of the γ phase is 40 μm or less, the length of the long side of the μ phase is 25 μm or less, and the κ phase exists in the α phase.

The free-cutting copper alloy according to the second aspect of the present invention is characterized in that the free-cutting copper alloy according to the first aspect of the present invention further contains Sb (antimony selected from 0.02 mass% to 0.08 mass%). ), Above 0.02mass% and One or more of As (arsenic) of 0.08 mass% or less and Bi (bismuth) of 0.02 mass% or more and 0.30 mass% or less.

The third aspect of the present invention is characterized in that the free-cutting copper alloy contains 75.5 mass% or more and 78.0 mass% or less of Cu, 3.1 mass% or more and 3.4 mass% or less of Si, 0.10 mass% or more and 0.27 mass% or more. The following Sn, P of 0.06 mass% to 0.13 mass%, and Pb of 0.024 mass% to 0.24 mass%, and the remainder includes Zn and unavoidable impurities. When the content of Cu is set to [Cu] mass When the content of Si is [Si] mass%, the content of Sn is [Sn] mass%, the content of P is [P] mass%, and the content of Pb is [Pb] mass% , Has the following relationship: 76.6 f1 = [Cu] + 0.8 × [Si] -8.5 × [Sn] + [P] + 0.5 × [Pb] 79.6, 61.7 f2 = [Cu] -4.3 × [Si] -0.7 × [Sn]-[P] + 0.5 × [Pb] 63.2 In the constituent phases of the metallurgical structure, the area ratio of the α phase is (α)%, the area ratio of the β phase is (β)%, and the area ratio of the γ phase is (γ) )%, The area ratio of the κ phase is (κ)%, and the area ratio of the μ phase is (μ)%, which has the following relationship: 30 (κ) 56,0 (γ) 0.8, (β) = 0, 0 (μ) 1.0, 98.0 f3 = (α) + (κ), 99.6 f4 = (α) + (κ) + (γ) + (μ), 0 f5 = (γ) + (μ) 1.5, 32 f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) 62, and the length of the long side of the γ phase is 30 μm or less, the length of the long side of the μ phase is 15 μm or less, and the κ phase exists in the α phase.

The free-cutting copper alloy according to the fourth aspect of the present invention is characterized in that the free-cutting copper alloy according to the third aspect of the present invention further contains Sb selected from more than 0.02 mass% to 0.07 mass%, and more than 0.02 One or two or more of As for mass% and 0.07mass% or less, and Bi for 0.02mass% or more and 0.20mass% or less.

The free-cutting copper alloy of the fifth aspect of the present invention is characterized in that, in the free-cutting copper alloy of any of the first to fourth aspects of the present invention, Fe (iron) ), Mn (manganese), Co (cobalt) and Cr (chromium) are less than 0.08 mass%.

The free-cutting copper alloy of the sixth aspect of the present invention is characterized in that, in the free-cutting copper alloy of any of the first to fifth aspects of the present invention, the amount of Sn contained in the κ phase is 0.08 mass% or more and 0.45 mass% or less, and the amount of P contained in the κ phase is 0.07 mass% or more and 0.24 mass% or less.

The seventh aspect of the present invention is characterized in that the free-cutting copper alloy has a Charpy impact test value in the free-cutting copper alloy in any of the first to sixth aspects of the present invention. Over 14 J / cm ² and less than 50 J / cm ² , tensile strength is 530 N / mm ² or more, and maintained at 150 ° C under a load equivalent to 0.2% proof stress at room temperature The creep strain after 100 hours is 0.4% or less. The Charpy impact test value is a value in a U-shaped notch-shaped test piece.

The free-cutting copper alloy according to the eighth aspect of the present invention is characterized in that the free-cutting copper alloy according to any of the first to seventh aspects of the present invention is used for water pipe appliances and industrial piping members. , Appliances that come into contact with liquids, automotive components, or electrical product components.

A method for manufacturing a free-cutting copper alloy according to a ninth aspect of the present invention is a method for manufacturing a free-cutting copper alloy according to any one of the first to eighth aspects of the present invention. The method is characterized by having cold working Either or both of the manufacturing process and the hot working process; and the annealing process performed after the aforementioned cold working process or the aforementioned hot working process; in the aforementioned annealing process, the temperature is maintained at a temperature of 510 ° C or higher and 575 ° C or lower for 20 minutes To 8 hours, or cooling at an average cooling rate of 0.1 ° C / min to 2.5 ° C / min in a temperature range of 575 ° C to 510 ° C, and then to exceed 2.5 ° C / min in a temperature range of 470 ° C to 380 ° C It is cooled at an average cooling rate of less than 500 ° C / minute.

A method for manufacturing a free-cutting copper alloy according to a tenth aspect of the present invention is a method for manufacturing a free-cutting copper alloy according to any one of the first to eighth aspects of the present invention. The method is characterized by including hot working. In the manufacturing process, the material temperature during hot working is 600 ° C to 740 ° C. When hot extrusion is performed as the aforementioned hot working, during the cooling process, cooling is performed at a temperature range of 470 ° C to 380 ° C at an average cooling rate of more than 2.5 ° C / min and less than 500 ° C / min. When hot forging is performed as the aforementioned hot working, during the cooling process, cooling is performed in a temperature range of 575 ° C to 510 ° C at an average cooling rate of 0.1 ° C / min or more and 2.5 ° C / min or less, and at 470 ° C to 380 ° C. The temperature range was cooled at an average cooling rate of more than 2.5 ° C / min and less than 500 ° C / min.

The method for producing a free-cutting copper alloy according to the eleventh aspect of the present invention is a method for producing a free-cutting copper alloy according to any one of the first to eighth aspects of the present invention. The method is characterized by having cold working Any one or both of the manufacturing process and the hot working process; and the low-temperature annealing process performed after the cold working process or the hot processing process; in the aforementioned low-temperature annealing process, when the material temperature is set to 240 ° C or higher and 350 The range is below ℃, the heating time is set to a range of 10 minutes to 300 minutes, the material temperature is set to T ° C, and the heating time is set to 150 minutes. (T-220) × (t) ^1/2 1200 conditions.

According to the aspect of the present invention, it is specified that the γ phase that is excellent in machinability but has poor corrosion resistance, impact characteristics, and high temperature strength (high temperature creep) is specified, and the metallurgical structure of the μ phase that is effective for machinability is reduced as much as possible. . The composition and manufacturing method for obtaining the metallographic structure are also specified. Therefore, according to this The bright aspect can provide a free-cutting copper alloy and a method for manufacturing a free-cutting copper alloy having excellent corrosion resistance, impact characteristics, ductility, wear resistance, normal temperature strength, and high-temperature strength under severe environments.

FIG. 1 is an electron micrograph of a microstructure of a free-cutting copper alloy (Test No. T05) in Example 1. FIG.

FIG. 2 is a metal micrograph of the structure of a free-cutting copper alloy (Test No. T53) in Example 1. FIG.

FIG. 3 is an electron micrograph of a microstructure of a free-cutting copper alloy (Test No. T53) in Example 1. FIG.

In FIG. 4, (a) is a metal micrograph of a cross section of Test No. T601 in Example 2 after 8 years of use in a severe water environment, and (b) is a dezincification corrosion test 1 of Test No. T602 The metal micrograph of the subsequent section, (c) is the metal micrograph of the section after the dezincification corrosion test 1 of Test No. T28.

Hereinafter, the free-cutting copper alloy and the manufacturing method of the free-cutting copper alloy according to the embodiments of the present invention will be described.

The free-cutting copper alloy of this embodiment is an electrical / automotive / mechanical / industrial piping used as a faucet, a valve, a joint, and the like for appliances, valves, joints, valves, and sliding components used in daily drinking water for humans and animals. Components, and liquids Contact with appliances, components and users.

Here, in this specification, a parenthesized element symbol such as [Zn] is set to indicate the content (mass%) of the element.

Furthermore, in this embodiment, a method of expressing the content is used to define a plurality of composition relational expressions as follows.

Composition relationship f1 = [Cu] + 0.8 × [Si] -8.5 × [Sn] + [P] + 0.5 × [Pb]

Composition relation f2 = [Cu] -4.3 × [Si] -0.7 × [Sn]-[P] + 0.5 × [Pb]

In addition, in the present embodiment, among the constituent phases of the metallurgical structure, the area ratio of the α phase is represented by (α)%, the area ratio of the β phase is represented by (β)%, and (γ) )% Indicates the area ratio of the γ phase, (κ)% indicates the area ratio of the κ phase, and (μ)% indicates the area ratio of the μ phase. In addition, the constituent phases of the metallographic structure mean that the α phase, the γ phase, and the κ are equal, and do not contain intermetallic compounds, precipitates, nonmetallic inclusions, and the like. The κ phase existing in the α phase is included in the area ratio of the α phase. The sum of the area ratios of all constituent phases is set to 100%.

In this embodiment, a plurality of organizational relational expressions are defined as follows.

Organization relation f3 = (α) + (κ)

Organization relation f4 = (α) + (κ) + (γ) + (μ)

Organization relation f5 = (γ) + (μ)

Organization relationship f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ)

The free-cutting copper alloy according to the first embodiment of the present invention contains 75.0 mass% to 78.5 mass% Cu, 2.95 mass% to 3.55 mass% Si, 0.07 mass% to 0.28 mass% Sn, P of 0.06 mass% or more and 0.14 mass% or less, and Pb of 0.022 mass% or more and 0.25 mass% or less, and the remainder includes Zn and unavoidable impurities. The composition relation f1 is set at 76.2 f1 In the range of 80.3, the composition relationship f2 is set at 61.5 f2 Within the range of 63.3. The area ratio of the κ phase is set at 25 (κ) In the range of 65, the area ratio of the γ phase is set to 0 (γ) Within the range of 1.5, the area ratio of the β phase is set at 0 (β) In the range of 0.2, the area ratio of the μ phase is set to 0 (μ) In the range of 2.0. The organizational relationship f3 is set at f3 In the range of 97.0, the organizational relationship f4 is set at f4 Within the range of 99.4, the organizational relationship f5 is set at 0 f5 Within the range of 2.5, the organizational relationship f6 is set at 27 f6 In the range of 70. The length of the long side of the γ phase is 40 μm or less, the length of the long side of the μ phase is 25 μm or less, and the k phase is present in the α phase.

The free-cutting copper alloy according to the second embodiment of the present invention contains 75.5 mass% or more and 78.0 mass% or less of Cu, 3.1 mass% or more and 3.4 mass% or less of Si, 0.10 mass% or more and 0.27 mass% or less of Sn, P of 0.06 mass% or more and 0.13 mass% or less, and Pb of 0.024 mass% or more and 0.24 mass% or less, and the remainder includes Zn and unavoidable impurities. The composition relation f1 is set at 76.6 f1 In the range of 79.6, the composition relationship f2 is set at 61.7 f2 Within 63.2. The area ratio of the κ phase is set at 30 (κ) Within the range of 56, the area ratio of the γ phase is set to 0 (γ) In the range of 0.8, the area ratio of the β phase is set to 0, and the area ratio of the μ phase is set to 0. (μ) Within the range of 1.0. The organizational relationship f3 is set at f3 Within the range of 98.0, the organizational relationship f4 is set at f4 Within the range of 99.6, the organizational relationship f5 is set at 0 f5 Within the range of 1.5, the organizational relationship f6 is set at 32 f6 Within 62. The length of the long side of the γ phase is 30 μm or less, the length of the long side of the μ phase is 15 μm or less, and the k phase is present in the α phase.

The free-cutting copper alloy according to the first embodiment of the present invention may further contain Sb selected from 0.02 mass% to 0.08 mass%, As, 0.02 mass% to 0.08 mass%, As, and 0.02 mass%. One or two or more Bis of 0.30 mass% or less.

In addition, the free-cutting copper alloy according to the second embodiment of the present invention may further contain Sb selected from more than 0.02 mass% to 0.07 mass%, As, and 0.02 mass% to 0.07 mass%. One or two or more Bis of 0.20 mass% or less.

In the free-cutting copper alloys according to the first and second embodiments of the present invention, the amount of Sn contained in the κ phase is 0.08 mass% or more and 0.45 mass% or less, and the amount of P contained in the κ phase is It is more preferably 0.07 mass% or more and 0.24 mass% or less.

Further, first and second embodiments of the present invention the free-cutting copper alloy, the Charpy impact test value exceeds 14J / cm ² and less than 50J / cm ^2, a tensile strength of 530N / mm ² or more, and loaded with It is preferable that the creep strain of the copper alloy after the copper alloy is kept at 150 ° C for 100 hours under the condition of 0.2% guaranteed stress (equivalent to a load of 0.2% guaranteed stress) at room temperature is 0.4% or less.

Hereinafter, the component composition and the composition relationship f1 are defined as described above. The reasons for f2, metallurgical structure, f3, f4, and f5 and mechanical characteristics will be explained.

<Ingredient composition>

(Cu)

Cu is the main element of the alloy of this embodiment, and in order to overcome the problem of the present invention, it is necessary to contain at least Cu in an amount exceeding 75.0 mass%. When the Cu content is less than 75.0 mass%, although the content varies according to the content of Si, Zn, and Sn, and the manufacturing process, the proportion of the γ phase exceeds 1.5%, resistance to dezincification, stress corrosion cracking resistance, impact characteristics, and extension Poor performance, normal temperature strength and high temperature strength (high temperature creep). In some cases, β-phase sometimes appears. Therefore, the lower limit of the Cu content is 75.0 mass% or more, preferably 75.5 mass% or more, and more preferably 75.8 mass% or more.

On the other hand, when the Cu content exceeds 78.5%, the cost increases due to the large amount of expensive copper used. Furthermore, not only the effects of corrosion resistance, normal temperature strength and high temperature strength are saturated, but also the proportion of the κ phase may become excessive. In addition, it is easy to precipitate a μ phase having a high Cu concentration, or in some cases, it is easy to precipitate a ζ phase and a χ phase. As a result, although it depends on the requirements of the metallographic structure, it may cause deterioration of machinability, impact characteristics, and hot workability. Therefore, the upper limit of the Cu content is 78.5 mass% or less, preferably 78.0 mass% or less, and even more preferably 77.5 mass% or less.

(Si)

In order to obtain many excellent characteristics of the alloy of this embodiment, the Si system is Required elements. Si contributes to the formation of κ phase, γ phase, and μ metal phases. Si improves the machinability, corrosion resistance, stress corrosion cracking resistance, strength, high temperature strength, and wear resistance of the alloy of this embodiment. Regarding the machinability, in the case of the α phase, the machinability is hardly improved even if Si is contained. However, since the γ phase, the κ phase, and the μ phase, which are formed by containing Si, are harder than the α phase, even if they do not contain a large amount of Pb, they can have excellent machinability. However, as the proportion of the γ phase or μ equivalent metal phase increases, the problems of decreased ductility and impact characteristics, the problem of reduced corrosion resistance in harsh environments, and the high temperature creep characteristics that can withstand long-term use cause problems. Therefore, it is necessary to define the κ phase, γ phase, μ phase, and β phase within appropriate ranges.

In addition, Si has the effect of significantly suppressing the evaporation of Zn during melting and casting. Further, as the Si content is increased, the specific gravity can be reduced.

In order to solve these problems of metallographic structure and satisfy all the various characteristics, although it depends on the content of Cu, Zn, Sn, etc., Si needs to contain 2.95 mass% or more. The lower limit of the Si content is preferably 3.05 mass% or more, more preferably 3.1 mass% or more, and still more preferably 3.15 mass% or more. On the surface, in order to reduce the proportion of the γ phase and the μ phase with a high Si concentration, it is considered that the Si content should be reduced. However, as a result of in-depth study of the blending ratio with other elements and the manufacturing process, it is necessary to specify the lower limit of the Si content as described above. Also, although it differs depending on the content of other elements, the relationship between the composition and the manufacturing process, the Si content is bounded by about 2.95 mass%, and there are slender needle-like kappa in the α phase. Phase, and the Si content is about 3.1 mass% as the boundary, the amount of needle-like κ phase increases. The kappa phase existing in the α phase improves tensile strength, machinability, impact characteristics, and abrasion resistance without impairing ductility. Hereinafter, the κ phase existing in the α phase is also referred to as a κ1 phase.

On the other hand, if the Si content is too large, the ductility and impact characteristics are emphasized in this embodiment, so that the κ phase, which is harder than the α phase, becomes excessive and becomes a problem. Therefore, the upper limit of the Si content is 3.55 mass% or less, preferably 3.45 mass% or less, more preferably 3.4 mass% or less, and still more preferably 3.35 mass% or less.

(Zn)

Zn, together with Cu and Si, are main constituent elements of the alloy of this embodiment, and are elements required to improve machinability, corrosion resistance, strength, and castability. In addition, although Zn exists as the remainder, if it is noted that the upper limit of the Zn content is about 21.7 mass% or less, and the lower limit is about 17.5 mass% or more.

(Sn)

Sn significantly improves dezincification and corrosion resistance, especially in harsh environments, and improves stress corrosion cracking resistance, machinability, and abrasion resistance. In a copper alloy including a plurality of metal phases (constituting phases), the corrosion resistance of each metal phase has advantages and disadvantages. Even if it eventually becomes two phases, an α phase and a κ phase, corrosion will begin from the phase with poor corrosion resistance and the corrosion will progress. Sn improves the corrosion resistance of the α phase, which is the most excellent corrosion resistance, and also improves the corrosion resistance of the κ phase, which is the second most excellent corrosion resistance. For Sn In other words, compared to the amount distributed in the α phase, the amount distributed in the κ phase is about 1.4 times. That is, the amount of Sn distributed in the κ phase is about 1.4 times the amount of Sn distributed in the α phase. As the amount of Sn increases, the corrosion resistance of the κ phase further increases. With the increase of the Sn content, the advantages and disadvantages of the corrosion resistance of the α phase and the κ phase almost disappear, or at least the difference between the corrosion resistance of the α phase and the κ phase is reduced, thereby greatly improving the corrosion resistance as an alloy.

However, the inclusion of Sn promotes the formation of the γ phase. Sn itself does not have an excellent machinability function, but by forming a γ phase having excellent machinability, the machinability of the alloy is improved as a result. On the other hand, the γ phase deteriorates the corrosion resistance, ductility, impact characteristics, ductility, and high-temperature strength of the alloy. Compared to the α phase, Sn is distributed about 10 times to about 17 times in the γ phase. That is, the amount of Sn distributed in the γ phase is about 10 times to about 17 times the amount of Sn distributed in the α phase. Compared with the γ phase not containing Sn, the γ phase containing Sn is insufficient to the extent that the corrosion resistance is slightly improved. In this way, although the corrosion resistance of the κ phase and the α phase is improved, the inclusion of Sn in the Cu-Zn-Si alloy promotes the formation of the γ phase. In addition, Sn is mostly distributed in the γ phase. Therefore, if the necessary elements such as Cu, Si, P, and Pb are not set to a more appropriate blending ratio and an appropriate metallurgical state including the manufacturing process, the inclusion of Sn will only slightly increase the κ phase and α phase. On the contrary, the increase in the γ phase causes the corrosion resistance, ductility, impact characteristics, and high temperature characteristics of the alloy to decrease. The inclusion of Sn in the κ phase improves the machinability of the κ phase. The effect is further increased as Sn is contained together with P.

By controlling the metallography including the relationship and the manufacturing process described below Microstructure can be made into a copper alloy with various characteristics. In order to exert this effect, the lower limit of the content of Sn needs to be 0.07 mass% or more, preferably 0.10 mass% or more, and more preferably 0.12 mass% or more.

On the other hand, if the Sn content exceeds 0.28 mass%, the proportion of the γ phase increases. As a countermeasure for this, it is necessary to increase the Cu concentration and increase the κ phase in the metallurgical structure, so that it may not be possible to obtain more favorable impact characteristics. The upper limit of the Sn content is 0.28 mass% or less, preferably 0.27 mass% or less, and more preferably 0.25 mass% or less.

(Pb)

Containing Pb improves the machinability of copper alloys. About 0.003 mass% of Pb is solid-melted in the base, and Pb exceeding this amount exists as Pb particles having a diameter of about 1 μm. Pb is effective for machinability even in a small amount, and especially when it exceeds 0.02 mass%, it starts to exhibit a remarkable effect. In the alloy of this embodiment, since the γ phase having excellent cutting performance is suppressed to 1.5% or less, a small amount of Pb is used instead of the γ phase.

Therefore, the lower limit of the content of Pb is 0.022 mass% or more, preferably 0.024 mass% or more, and still more preferably 0.025 mass% or more. In particular, when the value of the relational expression f6 of the metallographic structure related to machinability is less than 32, the content of Pb is preferably 0.024 mass% or more.

On the other hand, Pb is harmful to the human body and affects impact characteristics and high temperature strength. Therefore, the upper limit of the Pb content is 0.25 mass% or less, preferably 0.24 mass% or less, more preferably 0.20 mass% or less, and most preferably 0.10 mass%. the following.

(P)

P and Sn greatly improve the resistance to dezincification and stress corrosion cracking, especially in severe environments.

P is the same as Sn, and the amount distributed in the κ phase is approximately twice as much as that in the α phase. That is, the amount of P distributed in the κ phase is about twice the amount of P distributed in the α phase. In addition, the effect of P on improving the corrosion resistance of the α phase is significant, but the effect of improving the corrosion resistance on the κ phase is small when P is added alone. However, by coexisting with Sn, P can improve the corrosion resistance of the κ phase. Furthermore, P hardly improves the corrosion resistance of the γ phase. In addition, the inclusion of P in the κ phase slightly improves the machinability of the κ phase. Adding Sn and P together improves the machinability more effectively.

In order to exert these effects, the lower limit of the P content is 0.06 mass% or more, preferably 0.065 mass% or more, and more preferably 0.07 mass% or more.

On the other hand, even if P is contained in excess of 0.14 mass%, not only the effect of corrosion resistance is saturated, but also compounds of P and Si are easily formed. As a result, impact characteristics and ductility are deteriorated, and machinability is adversely affected. Therefore, the upper limit of the P content is 0.14 mass% or less, preferably 0.13 mass% or less, and more preferably 0.12 mass% or less.

(Sb, As, Bi)

Sb and As are the same as P and Sn, which further improve the resistance to dezincification and stress corrosion cracking, especially in harsh environments.

In order to improve corrosion resistance by containing Sb, it is necessary to contain 0.02 mass% The above Sb is preferably Sb in an amount exceeding 0.02 mass%. On the other hand, even if Sb is contained in excess of 0.08 mass%, the effect of improving the corrosion resistance is saturated, and γ is increased on the contrary. Therefore, the content of Sb is 0.08 mass% or less, and preferably 0.07 mass% or less.

In addition, in order to improve corrosion resistance by containing As, it is necessary to contain As of 0.02 mass% or more, and it is preferable to contain As in an amount exceeding 0.02 mass%. On the other hand, even if As is contained in excess of 0.08 mass%, the effect of improving the corrosion resistance is saturated. Therefore, the content of As is 0.08 mass% or less, and preferably 0.07 mass% or less.

By including Sb alone, the corrosion resistance of the α phase is improved. Sb is a low-melting-point metal with a higher melting point than Sn, showing similar tracks to Sn. Compared with the α phase, it is mostly distributed in the γ phase and the κ phase. Sb has the effect of improving the corrosion resistance of the κ phase by being added together with Sn. However, the effect of improving the corrosion resistance of the γ phase is small when Sb is contained alone or when Sb is contained together with Sn and P. Containing an excessive amount of Sb may cause an increase in the γ phase.

Among Sn, P, Sb, and As, As enhances the corrosion resistance of the α phase. Even if the κ phase is corroded, since the corrosion resistance of the α phase is improved, As plays a role of preventing the corrosion of the α phase that occurs in a chain reaction. However, the effect of improving the corrosion resistance of the κ phase and the γ phase is small when As is contained alone or when As is contained together with Sn, P, and Sb.

Furthermore, when Sb and As are contained together, even if the total content of Sb and As exceeds 0.10 mass%, the effect of improving the corrosion resistance will be saturated, which will delay the Reduced ductility and impact characteristics. Therefore, the total amount of Sb and As is preferably 0.10 mass% or less. In addition, Sb has the effect of improving the corrosion resistance of the κ phase as well as Sn. Therefore, if the amount of [Sn] + 0.7 × [Sb] exceeds 0.12 mass%, the corrosion resistance as an alloy is further improved.

Bi further improves the machinability of copper alloys. Therefore, it is necessary to contain Bi of 0.02 mass% or more, and it is preferable to contain Bi of 0.025 mass% or more. On the other hand, although the harmfulness of Bi to the human body is still uncertain, considering the impact on the impact characteristics and high-temperature strength, the upper limit of the content of Bi is set to 0.30 mass% or less, preferably 0.20 mass% or less. It is preferably at most 0.15 mass%, and more preferably at most 0.10 mass%.

(Unavoidable impurities)

Examples of the unavoidable impurities in this embodiment include Al, Ni, Mg, Se, Te, Fe, Co, Ca, Zr, Cr, Ti, In, W, Mo, B, Ag, and rare earth elements Wait.

For a long time, free-cutting copper alloys are mainly based on recycled copper alloys, rather than high-quality materials such as electrolytic copper and electrolytic zinc. In the next process (downstream process, processing process) in this field, most components and components are subjected to cutting processing, and a large amount of discarded copper alloy is produced at a ratio of 40 to 80 relative to the material 100. Examples include chips, cut edges, burrs, runners, and products that include poor manufacturing. These discarded copper alloys became the main raw materials. If the separation of cutting chips and the like is insufficient, Pb, Fe, Se, Te, Sn, P, Sb, As, Ca, Al, Zr, Ni and rare earth elements. The cutting chips include Fe, W, Co, Mo, and the like mixed in from the tool. Because the scrap contains electroplated products, it is mixed with Ni and Cr. Mg, Fe, Cr, Ti, Co, In, and Ni are mixed into pure copper-based scrap. From the perspective of resource reuse and cost considerations, waste materials such as chips containing these elements are used as raw materials to a certain extent within a range that does not adversely affect the characteristics. According to experience, most of Ni is mixed from waste materials, etc. The amount of Ni is allowed to be less than 0.06 mass%, and preferably less than 0.05 mass%. Fe, Mn, Co, Cr, etc. form an intermetallic compound with Si, and in some cases form an intermetallic compound with P, thereby affecting machinability. Therefore, the amounts of Fe, Mn, Co, and Cr are preferably less than 0.05 mass%, and more preferably less than 0.04 mass%. The total content of Fe, Mn, Co, and Cr is also preferably set to less than 0.08 mass%. The total amount is more preferably less than 0.07 mass%, and still more preferably less than 0.06 mass%. As the other elements, the respective amounts of Al, Mg, Se, Te, Ca, Zr, Ti, In, W, Mo, B, Ag, and rare earth elements are preferably less than 0.02 mass%, and less than 0.01 mass% are further preferable. .

The amount of rare earth elements is the total amount of one or more of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Tb, and Lu. .

(Composition relation f1)

The composition relationship formula f1 is a formula showing the relationship between the composition and the metallographic structure. Even if the amount of each element is within the above-mentioned range, if the composition relationship formula f1 is not satisfied, the various targets set in this embodiment cannot be satisfied. special Sex. In the composition relational expression f1, Sn is given a large coefficient of -8.5. If the composition relationship f1 is less than 76.2, no matter how much effort is spent on the manufacturing process, the proportion of the γ phase also increases, and the long side of the γ phase becomes longer, and the corrosion resistance, impact characteristics, and high temperature characteristics become worse. Therefore, the lower limit of the composition relational expression f1 is 76.2 or more, preferably 76.4 or more, more preferably 76.6 or more, and still more preferably 76.8 or more. As the composition relationship f1 becomes a better range, the area ratio of the γ phase decreases. Even if the γ phase exists, the γ phase tends to be divided, corrosion resistance, impact characteristics, ductility, strength at normal temperature, and high temperature characteristics. Further improve. If the value of the composition relational expression f1 is 76.6 or more, the slender needle-like κ phase (κ1 phase) becomes more prominent in the α phase by spending effort on the manufacturing process, and the tensile strength is improved without impairing ductility. Strength, machinability, and impact characteristics.

On the other hand, the upper limit of the composition relational expression f1 mainly affects the proportion of the κ phase. If the composition relational expression f1 is greater than 80.3, the proportion of the κ phase becomes excessive when the ductility and impact characteristics are valued. In addition, the μ phase becomes easily precipitated. When there are too many κ phases and μ phases, impact characteristics, ductility, high-temperature characteristics, hot workability, and corrosion resistance deteriorate. Therefore, the upper limit of the composition relational expression f1 is 80.3 or less, preferably 79.6 or less, and even more preferably 79.3 or less.

In this way, by setting the composition relationship f1 within the above range, a copper alloy having excellent characteristics can be obtained. In addition, regarding As, Sb, Bi and other unavoidable impurities as selected elements, considering their contents comprehensively, they hardly affect the composition relationship formula f1, so they are not specified in the composition relationship formula f1.

(Composition relation f2)

The composition relational expression f2 is a formula showing the relationship between composition and workability, various characteristics, and metallographic structure. If the composition relationship f2 is less than 61.5, the proportion of the γ phase in the metallurgical structure increases, and other metal phases, including the β phase, tend to appear and remain, which results in corrosion resistance, impact characteristics, cold workability, and high temperature. The creep characteristics deteriorate. Moreover, the crystal grains become coarse during hot forging, and cracks easily occur. Therefore, the lower limit of the composition relational expression f2 is 61.5 or more, preferably 61.7 or more, more preferably 61.8 or more, and even more preferably 62.0 or more.

On the other hand, if the composition relational expression f2 exceeds 63.3, the thermal deformation resistance increases and the thermal deformation ability decreases, and surface cracking may occur in hot extruded materials and hot forged products. Although it is also related to the hot working ratio and extrusion ratio, for example, hot working at about 630 ° C. and hot forging (both the temperature of the material immediately after hot working) are difficult. In addition, a coarse α phase having a length exceeding 300 μm and a width exceeding 100 μm in a direction parallel to the hot working direction tends to occur. When the coarse α phase is present, the machinability is reduced, the length of the long side of the α phase and the γ phase existing at the boundary of the κ phase is increased, and the strength and abrasion resistance are also decreased. In addition, the solidification temperature range (liquid phase temperature-solidus temperature) exceeds 50 ° C., shrinkage cavities during casting become remarkable, and sound casting cannot be obtained. Therefore, the upper limit of the composition relational expression f2 is 63.3 or less, preferably 63.2 or less, and more preferably 63.0 or less.

As described above, by setting the composition relationship f2 within a narrow range as described above, a copper alloy having excellent characteristics can be produced at a good yield. In addition, regarding As, Sb, Bi and other unavoidable impurities as selected elements, considering their contents comprehensively, it hardly affects the composition relationship formula f2, so it is not specified in the composition relationship formula f2.

(Compared with patent literature)

Here, Table 1 shows the results of comparing the compositions of the Cu-Zn-Si alloys described in Patent Documents 3 to 9 and the alloys of the present embodiment.

This embodiment differs from Patent Document 3 in the content of Pb and Sn as a selective element. This embodiment differs from Patent Document 4 in the content of Sn as a selective element. This embodiment differs from Patent Document 5 in the content of Pb. This embodiment differs from Patent Documents 6 and 7 in whether or not Zr is contained. This embodiment differs from Patent Document 8 in whether Fe is contained. This embodiment differs from Patent Document 9 in whether or not Pb is contained, and also in whether Fe, Ni, and Mn are contained.

As described above, the alloys of this embodiment have different composition ranges from the Cu-Zn-Si alloys described in Patent Documents 3 to 9.

<Metallographic structure>

Cu-Zn-Si alloy has more than 10 kinds of phases, and complex phase transitions will occur. The target characteristics may not necessarily be obtained only by the composition range and the relationship between elements. Finally, by specifying and determining the types and ranges of the metal phases present in the metallographic structure, the target characteristics can be obtained.

In the case of a Cu-Zn-Si alloy composed of a plurality of metal phases, the corrosion resistance of each phase is not the same and there are advantages and disadvantages. Corrosion progresses from the phase with the lowest corrosion resistance, that is, the phase that is most susceptible to corrosion, or from the boundary between the phase with poor corrosion resistance and the phase adjacent to the phase. In the case of a Cu-Zn-Si alloy including three elements of Cu, Zn, and Si, for example, if an α phase, an α 'phase, a β (including β') phase, a κ phase, and a γ (including γ ') phase And μ-phase corrosion resistance, the order of corrosion resistance from superior phase is α phase>α'phase> κ phase> μ phase γ phase> β phase. The difference in corrosion resistance between the κ phase and the μ phase is particularly large.

Here, the numerical value of the composition of each phase varies depending on the composition of the alloy and the occupied area ratio of each phase, and it can be said as follows.

The order of the Si concentration of each phase from high to low is μ phase> γ phase> κ phase> α phase> α 'phase β-phase. The Si concentration in the μ phase, γ phase, and κ phase is higher than that of the alloy. The Si concentration in the μ phase is about 2.5 to about 3 times the Si concentration in the α phase, and the Si concentration in the γ phase is about 2 to about 2.5 times the Si concentration in the α phase.

The Cu concentration of each phase is from μ concentration to κ phase in order from high to low. α phase> α 'phase γ phase> β phase. The Cu concentration in the μ phase is higher than that of the alloy.

In the Cu-Zn-Si alloys shown in Patent Documents 3 to 6, the γ phase having the best machinability function mainly coexists with the α 'phase, or exists in the boundary between the κ phase and the α phase. The γ phase selectively becomes a source of corrosion (origin of corrosion) under the harsh water quality or environment for copper alloys, and the corrosion progresses. Of course, if the β phase is present, the β phase begins to corrode before the γ phase corrodes. When the μ phase and the γ phase coexist, the corrosion of the μ phase starts slightly later or almost simultaneously than the γ phase. For example, when α phase, κ phase, γ phase, and μ phase coexist, if the γ phase and μ phase are selectively dezincified and corroded, the corroded γ phase and μ phase become Cu-rich by dezincification. Corrosion products that corrode the κ phase or the adjacent α 'phase, and the corrosion chain progresses reactively.

Furthermore, the quality of drinking water around the world, including Japan, is diverse, and its water quality has gradually become the quality of copper alloys that are easily corroded. For example, although it has an upper limit, the concentration of residual chlorine used for sterilization purposes increases due to safety issues to the human body, and the copper alloy as a water pipe appliance becomes a corrosive environment. As with the use environment of the automobile components, mechanical components, and industrial piping components, the corrosion resistance in the use environment containing many solutions can be said to be the same as drinking water.

On the other hand, even if the amount of the γ phase or γ phase, μ phase, and β phase is controlled, That is, the existence ratio of these phases is greatly reduced or eliminated, and the corrosion resistance of the Cu-Zn-Si alloy composed of three phases of α phase, α 'phase, and κ phase is not foolproof. Depending on the corrosive environment, the κ phase, which has a lower corrosion resistance than the α phase, may be selectively corroded, and the corrosion resistance of the κ phase needs to be improved. Furthermore, if the κ phase is corroded, the corroded κ phase becomes a corrosion product rich in Cu and corrodes the α phase. Therefore, it is also necessary to improve the corrosion resistance of the α phase.

In addition, since the γ phase is a hard and brittle phase, when a large load is applied to a copper alloy member, it becomes a source of stress concentration on a microscopic scale. Therefore, the γ phase increases the susceptibility to stress corrosion cracking, reduces the impact characteristics, and further reduces the high temperature strength (high temperature creep strength) through the high temperature creep phenomenon. The μ phase mainly exists at the grain boundary of the α phase, the phase boundary of the α phase, and the κ phase, and therefore becomes the source of microscopic stress concentration in the same way as the γ phase. By becoming a stress concentration source or grain boundary slip phenomenon, the μ phase increases the sensitivity to stress corrosion cracking, reduces impact characteristics, and reduces high temperature strength. In some cases, the presence of the μ phase deteriorates these various characteristics to a degree greater than the γ phase.

However, if the γ phase or the ratio of the γ phase to the μ phase is greatly reduced or eliminated in order to improve the corrosion resistance and the aforementioned various characteristics, only by containing a small amount of three phases: Pb and α phase, α ′ phase, and κ phase, Satisfactory machinability may not be obtained. Therefore, in order to improve the corrosion resistance, ductility, impact characteristics, strength, and high-temperature strength under the severe use environment on the premise that it contains a small amount of Pb and has excellent machinability, it is necessary to specify the structure of the metallurgical structure as follows. Phase formation (metal phase, crystalline phase).

In the following, the unit of the ratio (existence ratio) occupied by each phase is the area ratio (area%).

(γ phase)

The γ phase is the phase that contributes most to the machinability of the Cu-Zn-Si alloy. However, in order to make the corrosion resistance, strength, high temperature characteristics, and impact characteristics excellent in harsh environments, the γ phase has to be limited. In order to make the corrosion resistance excellent, it is necessary to contain Sn, but the addition of Sn further increases the γ phase. In order to satisfy these contradictory phenomena, that is, machinability and corrosion resistance, the content of Sn and P, the composition relationship formulas f1 and f2, the organization relationship formula described later, and the manufacturing process are limited.

(β-phase and other phases)

In order to obtain high ductility, impact properties, strength, and high-temperature strength by obtaining good corrosion resistance, the ratio of β phase, γ phase, μ phase, and ζ equal to other phases in the metallurgical structure is particularly important.

The proportion of the β phase needs to be at least 0% to 0.2%, and preferably 0.1% or less, and most preferably, the β phase does not exist.

The proportion of ζ other than the α phase, the κ phase, the β phase, the γ phase, and the μ phase is equal to the proportion of other phases, preferably 0.3% or less, and more preferably 0.1% or less. Most preferably, there are no other phases equal to zeta.

First, in order to obtain excellent corrosion resistance, it is necessary to set the ratio of the γ phase to 0% to 1.5%, and to set the length of the long side of the γ phase. It is set to 40 μm or less.

The length of the long side of the γ phase was measured by the following method. For example, the maximum length of the long side of the γ phase is measured in one field of view using a metal micrograph of 500 times or 1000 times. As described later, this operation is performed in a plurality of arbitrary fields of view, such as five fields of view. An average value of the maximum lengths of the long sides of the γ phase obtained in each field of view was calculated and used as the length of the long sides of the γ phase. Therefore, the length of the long side of the γ phase can also be said to be the maximum length of the long side of the γ phase.

The ratio of the γ phase is preferably 1.0% or less, more preferably 0.8% or less, and most preferably 0.5% or less. Although it varies depending on the content of Pb and the proportion of κ phase, for example, when the content of Pb is 0.03 mass% or less, or the proportion of κ phase is 33% or less, the amount is 0.05% or more and less than 0.5%. The existence of γ has a smaller influence on various characteristics such as corrosion resistance, and can improve machinability.

Since the length of the long side of the γ phase affects the corrosion resistance, the length of the long side of the γ phase is 40 μm or less, preferably 30 μm or less, and more preferably 20 μm or less.

The larger the amount of the γ phase, the easier the γ phase is selectively corroded. Also, the longer the γ phase continues, the easier it is to selectively corrode accordingly, and the faster the corrosion progresses in the depth direction. In addition, the more the corroded portion, the more the corrosion resistance of the α 'phase, the κ phase, and the α phase existing around the corroded γ phase is affected.

The proportion of the γ phase and the length of the long side of the γ phase and Cu, Sn, Si The relationship between the content and composition of f1 and f2 is very relevant.

The more the γ phase, the worse the ductility, impact characteristics, high temperature strength, and stress corrosion cracking resistance. Therefore, the γ phase needs to be 1.5% or less, preferably 1.0% or less, and more preferably 0.8% or less. , The best is below 0.5%. The γ phase existing in the metallographic structure becomes a stress concentration source when a high stress is loaded. When the crystal structure of the γ phase is BCC, high-temperature strength is reduced, and impact characteristics and stress corrosion cracking resistance are reduced. Among them, when the proportion of the κ phase is 30% or less, there are some problems in machinability. As a small amount that affects corrosion resistance, impact characteristics, ductility, and high-temperature strength, a γ phase of about 0.1% may exist. In addition, the γ phase of 0.1% to 1.2% improves abrasion resistance.

(μphase)

Although the μ phase has the effect of improving machinability, it is necessary to set the proportion of the μ phase to be at least 0% and 2.0% in terms of affecting corrosion resistance, ductility, impact characteristics, and high temperature characteristics. The proportion of the μ phase is preferably 1.0% or less, more preferably 0.3% or less, and the absence of the μ phase is most preferable. The μ phase mainly exists at grain boundaries and phase boundaries. Therefore, in the harsh environment, grain boundary corrosion occurs at the grain boundary where the μ phase exists. When an impact action is applied, cracks are likely to occur starting from the hard μ phase existing at the grain boundaries. In addition, for example, when a copper alloy is used in a valve for turning an engine of a car or a high-temperature and high-pressure gas valve, it is performed at a high temperature of 150 ° C for a long time. If it is maintained, the grain boundaries are liable to cause slippage and creep. Therefore, it is necessary to limit the amount of the μ phase and to set the length of the long side of the μ phase mainly existing at the grain boundary to 25 μm or less. The length of the long side of the μ phase is preferably 15 μm or less, more preferably 5 μm or less, even more preferably 4 μm or less, and most preferably 2 μm or less.

The length of the long side of the μ phase can be measured by the same method as the method of measuring the long side of the γ phase. That is, depending on the size of the μ phase, for example, a 500-times or 1000-times metal photomicrograph or a 2000-times or 5000-times secondary electron image photograph (electron micrograph) is used to determine the μ-phase in one field of view. The maximum length of the long side. This operation is performed in a plurality of arbitrary fields of view, such as five fields of view. The average value of the maximum lengths of the long sides of the μ-phase obtained in each field of view was calculated and used as the length of the long sides of the μ-phase. Therefore, the length of the long side of the μ phase can be said to be the maximum length of the long side of the μ phase.

(κphase)

Under recent high-speed cutting conditions, the cutting performance of materials including cutting resistance and chip discharge is important. However, in a state where the ratio of the γ phase having the most excellent machinability function is limited to 1.5% or less, in order to have particularly excellent machinability, the ratio of the κ phase needs to be at least 25% or more. The proportion of the κ phase is preferably 30% or more, more preferably 32% or more, and most preferably 34% or more. In addition, if the proportion of the κ phase is a minimum amount that satisfies the machinability, the ductility is rich, the impact characteristics are excellent, and the corrosion resistance, high temperature characteristics, and abrasion resistance become good.

The proportion of the hard κ phase increases, the machinability increases, and the tensile strength increases. However, on the other hand, as the κ phase increases, the ductility and impact characteristics gradually decrease. In addition, if the proportion of the κ phase reaches a certain constant amount, the effect of improving the machinability is also saturated, and if the κ phase increases, the machinability decreases. When the proportion of the κ phase reaches a certain constant amount, as the ductility decreases, the tensile strength becomes saturated, and the cold workability and hot workability also deteriorate. In consideration of reduction in ductility, impact properties, and machinability, the proportion of the κ phase needs to be 65% or less. That is, the ratio of the κ phase in the metallographic structure needs to be approximately 2/3 or less. The proportion of the κ phase is preferably 56% or less, more preferably 52% or less, and most preferably 48% or less.

In order to obtain excellent machinability while limiting the area ratio of the γ phase having excellent cutting performance to 1.5% or less, it is necessary to improve the machinability of the κ phase and the α phase. That is, by including Sn, P in the κ phase, the machinability of the κ phase is improved. The presence of the needle-like κ phase in the α phase improves the machinability of the α phase, but greatly reduces the ductility and improves the machinability of the alloy. As the proportion of the κ phase in the metallurgical structure, in order to have all the ductility, strength, impact characteristics, corrosion resistance, high temperature characteristics, machinability, and wear resistance, it is preferably about 33% to 52%.

(Presence of slender needle-like κ phase (κ1 phase) in α phase)

If the above-mentioned composition, composition relationship, and process requirements are satisfied, a needle-like κ phase will exist in the α phase. This κ is harder than the α phase. The κ phase in the α phase The (κ1 phase) has a thickness of about 0.1 μm to about 0.2 μm (about 0.05 μm to about 0.5 μm). The κ phase (κ1 phase) is thin, slender, and needle-shaped. By having a thin and long acicular κ phase (κ1 phase) in the α phase, the following effects can be obtained.

1) The α phase is strengthened, and the tensile strength as an alloy is improved.

2) The machinability of the α phase is improved, and machinability such as cutting resistance and chip splitting ability are improved.

3) Since it exists in the α phase, it does not adversely affect the corrosion resistance.

4) The α phase is enhanced, and the abrasion resistance is improved.

The needle-like κ phase existing in the α phase affects the constituent elements and relational expressions such as Cu, Zn, and Si. In particular, if the amount of Si is about 2.95% or more, a needle-like κ phase (κ1 phase) starts to exist in the α phase. When the amount of Si is about 3.05% or more than 3.1%, a more significant amount of the κ1 phase is present in the α phase. When the composition relational expression f2 is 63.0 or less and further 62.5 or less, the κ1 phase becomes more likely to exist.

A metal microscope with a magnification of about 500 times or about 1000 times can be used to confirm the slender needle-like kappa phase (κ1 phase) that is precipitated in the α phase and has a thin thickness. However, since it is difficult to calculate the area ratio, the κ1 phase in the α phase is the one included in the α phase.

(Organizational relations f3, f4, f5, f6)

In addition, in order to obtain excellent corrosion resistance, impact characteristics, and high-temperature strength, It is necessary that the total of the proportions of the α phase and the κ phase (organization relationship f3 = (α) + (κ)) is 97.0% or more. The value of f3 is preferably 98.0% or more, more preferably 98.5% or more, and most preferably 99.0% or more. Similarly, the total of the proportions of α phase, κ phase, γ phase, and μ phase (organization relationship f4 = (α) + (κ) + (γ) + (μ)) is 99.4% or more, and preferably 99.6 %the above.

In addition, the total ratio (f5 = (γ) + (μ)) of the γ phase and the μ phase is required to be 2.5% or less. The value of f5 is preferably 1.5% or less, more preferably 1.0% or less, and most preferably 0.5% or less. Among them, when the proportion of the κ phase is low, the machinability is slightly problematic. Therefore, it does not prevent the γ phase from being contained in an amount of about 0.05 to 0.5% to such an extent that the impact characteristics are not excessively affected.

Here, in the relational expressions f3 to f6 of the metallographic structure, there are ten kinds of metal phases: α phase, β phase, γ phase, δ phase, ε phase, ζ phase, η phase, κ phase, μ phase, and χ phase. For the purpose, intermetallic compounds, Pb particles, oxides, non-metallic inclusions, unmelted substances, etc. are not targeted. Needle-like kappa phases existing in the α phase are included in the α phase, and μ phases that are not observed in a metal microscope are excluded. Furthermore, intermetallic compounds formed by Si, P, and unavoidably mixed elements (for example, Fe, Co, Mn) are outside the applicable range of the metal phase area ratio. However, since these intermetallic compounds affect machinability, attention must be paid to unavoidable impurities.

(Organizational relationship f6)

In the alloy of this embodiment, Cu-Zn-Si alloy The content is kept to a minimum, and the machinability is also good. In particular, it is necessary to satisfy all excellent corrosion resistance, impact characteristics, ductility, normal temperature strength, and high temperature strength. However, the machinability is incompatible with the excellent corrosion resistance and impact characteristics.

From the perspective of metallographic structure, the more the γ phase with the best cutting performance is included, the better the machinability, but the γ phase has to be reduced in terms of corrosion resistance, impact characteristics and other characteristics. It was found that when the proportion of the γ phase is 1.5% or less, in order to obtain good machinability, it is necessary to set the value of the above-mentioned microstructure relation f6 within an appropriate range according to the experimental results.

The γ phase has the best cutting performance, but especially when the γ phase is small, that is, when the γ phase rate is 1.5% or less, a coefficient that is 6 times higher than the ratio of the κ phase ((κ)) is provided to the γ phase. The value of the square root of the proportion ((γ) (%)). In order to obtain good cutting performance, the structural relationship f6 needs to be 27 or more. The value of f6 is preferably 32 or more, and more preferably 34 or more. When the value of the structural relationship f6 is 28 to 32, in order to obtain excellent cutting performance, it is preferable that the content of Pb is 0.024 mass% or more, or the amount of Sn contained in the κ phase is 0.11 mass% or more.

On the other hand, if the organization relational expression f6 exceeds 62 or 70, the machinability will worsen, and the impact characteristics and ductility will obviously deteriorate. Therefore, the organizational relationship f6 needs to be 70 or less. The value of f6 is preferably 62 or less, and more preferably 56 or less.

(Amounts of Sn and P contained in the κ phase)

In order to improve the corrosion resistance of the κ phase, Sn is preferably contained in the alloy in an amount of 0.07 mass% or more and 0.28 mass% or less, and P is contained in an amount of 0.06 mass% or more and 0.14 mass% or less.

In the alloy of this embodiment, when the Sn content is 0.07 to 0.28 mass%, and when the amount of Sn distributed in the α phase is set to 1, Sn is about 1.4 in the κ phase and about 10 to about 17 in the γ phase. The ratio of about 2 to about 3 in the μ phase is distributed. By investing effort in the manufacturing process, the amount of distribution in the γ phase can be reduced to about 10 times the amount of distribution in the α phase. For example, in the case of the alloy of this embodiment, the proportion of α phase in a Cu-Zn-Si-Sn alloy containing Sn of 0.2 mass% is 50%, and the proportion of κ phase is 49% When the proportion of γ phase is 1%, the Sn concentration in the α phase is about 0.15 mass%, the Sn concentration in the κ phase is about 0.22 mass%, and the Sn concentration in the γ phase is about 1.8 mass%. Furthermore, if the area ratio of the γ phase is large, the amount of Sn consumed in the γ phase increases, and the amount of Sn distributed in the κ phase and the α phase decreases. Therefore, if the amount of the γ phase is reduced, as described later, Sn is effectively used for corrosion resistance and machinability.

On the other hand, when the amount of P distributed in the α phase is set to 1, P is distributed at a ratio of about 2 in the κ phase, about 3 in the γ phase, and about 3 in the μ phase. For example, in the case of the alloy of this embodiment, the proportion of the α phase in the Cu-Zn-Si alloy containing 0.1 mass% of P is 50% and the ratio of the κ phase For example, when the ratio is 49% and the proportion of γ phase is 1%, the P concentration in the α phase is about 0.06 mass%, the P concentration in the κ phase is about 0.12 mass%, and the P concentration in the γ phase is about 0.18 mass. %.

Both Sn and P improve the corrosion resistance of the α phase and the κ phase, but compared to the amounts of Sn and P contained in the α phase, the amounts of Sn and P contained in the κ phase are about 1.4 times and about 2 times, respectively. Times. That is, the amount of Sn contained in the κ phase is about 1.4 times the amount of Sn contained in the α phase, and the amount of P contained in the κ phase is about 2 times the amount of P contained in the α phase. Therefore, the degree of improvement in the corrosion resistance of the κ phase is superior to the degree of improvement in the corrosion resistance of the α phase. As a result, the corrosion resistance of the κ phase is close to that of the α phase. In addition, by adding Sn and P together, the corrosion resistance of the κ phase can be particularly improved. However, including the difference in content, the contribution of Sn to the corrosion resistance is greater than P.

When the content of Sn is less than 0.07 mass%, the corrosion resistance and dezincification resistance of the κ phase are inferior to that of the α phase and the dezincification corrosion resistance. Therefore, in poor water quality, the κ phase may be selectively corrosion. The more distribution of Sn in the κ phase will improve the corrosion resistance of the κ phase, which is worse than that of the α phase, and make the corrosion resistance of the κ phase containing Sn at a certain concentration more than that of the α phase. At the same time, when Sn is contained in the κ phase, the machinability of the κ phase is improved and the wear resistance is improved. Therefore, the Sn concentration in the κ phase is preferably 0.08 mass% or more, more preferably 0.11 mass% or more, and still more preferably 0.14 mass% or more.

On the other hand, Sn is mostly distributed in the γ phase, but even in the γ phase Containing a large amount of Sn is also mainly due to the reason that the crystal structure of the γ phase is the BCC structure, so the corrosion resistance of the γ phase is hardly improved. Moreover, if the proportion of the γ phase is large, the amount of Sn distributed in the κ phase is reduced, and thus the degree of improvement in the corrosion resistance of the κ phase is reduced. When the proportion of the γ phase decreases, the amount of Sn distributed in the κ phase increases. If a large amount of Sn is distributed in the κ phase, the corrosion resistance and cutting performance of the κ phase are improved, and the loss of machinability of the γ phase can be compensated. As a result of containing more than a predetermined amount of Sn in the κ phase, it is considered that the machinability of the κ phase itself and the chip-splitting performance are improved. However, if the Sn concentration in the κ phase exceeds 0.45 mass%, the machinability of the alloy is improved, but the toughness of the κ phase begins to be impaired. If toughness is more important, the upper limit of the Sn concentration in the κ phase is preferably 0.45 mass% or less, more preferably 0.40 mass% or less, and still more preferably 0.35 mass% or less.

On the other hand, if the content of Sn is increased, it becomes difficult to reduce the amount of the γ phase in consideration of the relationship with other elements, Cu, and Si. In order to set the ratio of the γ phase to 1.5% or less and further 0.8% or less, it is necessary to set the Sn content in the alloy to 0.28 mass% or less, and it is preferable to set the Sn content to 0.27 mass% or less.

As with Sn, if P is mostly distributed in the κ phase, the corrosion resistance is improved and the machinability of the κ phase is improved. Among them, when excessive P is contained, it is consumed in the Si-forming intermetallic compound to deteriorate the characteristics, or excessive solid solution melting impairs the impact characteristics and ductility. P concentration in κ phase The lower limit of the degree is preferably 0.07 mass% or more, and more preferably 0.08 mass% or more. The upper limit of the P concentration in the κ phase is preferably 0.24 mass% or less, more preferably 0.20 mass% or less, and still more preferably 0.16 mass% or less.

<Features>

(Normal temperature strength and high temperature strength)

As strength required in various fields including valves, appliances, and automobiles for drinking water, tensile strength suitable for the breaking stress of a pressure vessel is considered important. In addition, for example, a valve or a high-temperature / high-pressure valve used in an environment close to the engine room of a car is used in a temperature environment up to 150 ° C. However, it is of course required that the valve is not deformed or damaged when stress is applied. In the case of a pressure vessel, its allowable stress affects the tensile strength.

For this reason, as a hot-extruded material and a hot-forged material of a hot working material, a high-strength material having a tensile strength of 530 N / mm ² or more at normal temperature is preferable. The tensile strength at room temperature is preferably 550 N / mm ² or more. In essence, hot forging materials are generally not cold worked.

On the other hand, in some cases, the strength of the hot-worked material is increased by cold drawing or drawing. In the alloy according to this embodiment, when the cold working ratio is 15% or less when cold working is performed, each 1% increase in the cold working ratio increases the tensile strength by about 12 N / mm ² . In contrast, for every 1% reduction in cold working rate, the impact characteristics are reduced by about 4% or 5%. For example, when an alloy material with a tensile strength of 560 N / mm ² and an impact value of 30 J / cm ² is subjected to cold drawing at a cold working rate of 5% to produce a cold-worked material, the cold-worked material has a tensile strength of about 620 N / mm ² , The impact value is approximately 23 J / cm ² . If the cold working rates are different, the tensile strength and impact value cannot be uniquely determined.

On the other hand, when drawing, cold working of a wire, and subsequent heat treatment under appropriate conditions, both tensile strength and impact characteristics are improved compared to hot extruded materials. By cold working, the strength is increased and the impact characteristics are reduced. By heat treatment, the γ phase decreases and the proportion of the κ phase increases, and a needle-like κ phase exists in the α phase. The α and κ phases of the base were restored. As a result, compared with hot extrusion materials, corrosion resistance, tensile strength, and impact value are greatly improved, and alloys with higher strength and toughness are made.

Regarding the high temperature strength, it is preferable that the latent strain system after holding the copper alloy at 150 ° C for 100 hours under a stress equivalent to 0.2% of the guaranteed stress at room temperature is 0.4% or less. This creep change should preferably be 0.3% or less, and more preferably 0.2% or less. In this case, even if exposed to a high temperature such as a high-temperature and high-pressure valve, a valve material close to an engine room of an automobile, etc., it is not easily deformed and has excellent high-temperature strength.

In addition, the tensile strength of hot extruded materials and hot-forged products at room temperature in the case of free-cutting brasses containing 60 mass% Cu and 3 mass% Pb and the rest including Zn and unavoidable impurities containing Pb 360N / mm ² to 400N / mm ² . In addition, even when the alloy is loaded with a stress equivalent to 0.2% of the guaranteed stress at room temperature, after exposing the alloy at 150 ° C for 100 hours, the creep strain is about 4 to 5%. Therefore, compared with the conventional free-cutting brass containing Pb, the tensile strength and heat resistance of the alloy of this embodiment are higher. That is, the alloy of the present embodiment has high strength at room temperature, and hardly deforms even if it is exposed to high temperature for a long period of time when the high strength is added. Therefore, thinning and weight reduction can be achieved by high strength. In particular, in the case of forged materials such as high-pressure valves, cold working cannot be performed. Therefore, high strength is used to achieve high performance, thinning, and weight reduction.

The high-temperature characteristics of the alloy of this embodiment are also substantially the same for extruded materials and materials subjected to cold working. That is, by implementing cold working, the 0.2% guaranteed stress is increased, but even when a load equivalent to a higher 0.2% guaranteed stress is applied, the creep strain of the alloy after exposure to 150 ° C for 100 hours is 0.4. % Or less and has high heat resistance. The high temperature characteristics mainly affect the area ratios of the β phase, the γ phase, and the μ phase. The higher the area ratio, the worse the high temperature characteristics become. Further, as the lengths of the long sides of the μ phase and the γ phase existing at the grain boundaries and phase boundaries of the α phase become longer, the high temperature characteristics become worse.

(Impact resistance)

Generally, it becomes brittle when the material has high strength. A material that is excellent in chip separation during cutting is considered to have some kind of brittleness. Impact characteristics are contradictory to machinability and strength in some respects.

However, when copper alloys are used in various components such as drinking water appliances such as valves, joints, and valves, automotive components, mechanical components, and industrial piping, copper alloys need not only high strength but also impact resistance. Specifically, when a Charpy impact test with U-shaped recess oral tablets, Charpy impact value is preferably more than 14J / cm ^2, more preferably 17J / cm ² or more. In particular, for each heat-treated material such as hot-forged materials and extruded materials that have not been cold-worked, when a Charpy impact test is performed using a U-shaped notch test piece, the Charpy impact test value is preferably 17 J / cm ² or more, and more preferably 20 J / cm ² or more, and more preferably 24 J / cm ² or more. The alloy of this embodiment is an alloy having excellent machinability, and even if the application is considered, the Charpy impact test value does not need to exceed 50 J / cm ² . If the Charpy impact test value exceeds 50 J / cm ² , the toughness will increase on the contrary, so the cutting resistance will increase, and the chipability will be deteriorated, such as the chips becoming easier to connect. Therefore, the Charpy impact test value is preferably less than 50 J / cm ² .

When the hard κ phase is increased or the Sn concentration in the κ phase is increased, the strength and machinability are improved, but the toughness, that is, the impact characteristics is decreased. Therefore, strength, machinability, and toughness (impact characteristics) are contradictory characteristics. The strength index with impact characteristics added to the strength is defined by the following formula.

(Strength Index) = (tensile strength) + 25 × (Charpy impact value) ^1/2

Regarding hot-worked materials (hot-extruded materials, hot-forged materials) and cold-worked materials that have undergone mild cold working with a processing rate of about 10%, if the strength index is 670 or more, it can be said that they are high-strength and tough materials . The strength index is preferably 680 or more, and more preferably 690 or more.

The impact characteristics are closely related to the metallographic structure, and the γ phase makes the impact particularly Sexual deterioration. In addition, if the μ phase exists at the grain boundary of the α phase, the phase boundary of the α phase, the κ phase, and the γ phase, the grain boundary and the phase boundary become brittle and the impact characteristics deteriorate.

As a result of the study, it was found that if a μ phase having a longer side length of more than 25 μm exists at the grain boundary and the phase boundary, the impact characteristics are particularly deteriorated. Therefore, the length of the long side of the existing μ phase is 25 μm or less, preferably 15 μm or less, more preferably 5 μm or less, and most preferably 2 μm or less. In addition, compared with the α phase and the κ phase, the μ phase existing at the grain boundary is easily corroded in a severe environment to cause grain boundary corrosion, and deteriorates the high temperature characteristics.

Furthermore, in the case of the μ phase, if the occupation ratio is reduced, and the length of the μ phase is short and the width is narrowed, it becomes difficult to confirm in a metal microscope with a magnification of about 500 or 1000 times. When the length of the μ phase is 5 μm or less, when observed with an electron microscope with a magnification of 2000 or 5000, the μ phase may sometimes be observed at the grain boundaries and phase boundaries.

<Manufacturing process>

Next, a method for manufacturing a free-cutting copper alloy according to the first and second embodiments of the present invention will be described.

The metallographic structure of the alloy of this embodiment changes not only in the composition but also in the manufacturing process. Not only affects the hot working temperature, heat treatment temperature and heat treatment conditions of hot extrusion, hot forging, but also the average cooling rate during the cooling process of hot work and heat treatment. As a result of in-depth research, the cooling process in hot working and heat treatment was learned In the metallographic structure, the cooling rate in the temperature range of 470 ° C to 380 ° C and the average cooling rate in the temperature range of 575 ° C to 510 ° C, especially 570 ° C to 530 ° C are greatly affected.

The manufacturing process of this embodiment is a necessary process for the alloy of this embodiment, and has a balance with the composition, but basically exhibits the following important effects.

1) Reduce the γ phase which deteriorates the corrosion resistance and impact characteristics, and reduce the length of the long side of the γ phase.

2) Control the μ phase that deteriorates the corrosion resistance and impact characteristics, and control the length of the long side of the μ phase.

3) The needle-like κ phase is separated into the α phase.

4) The amount (concentration) of Sn solidified in the κ phase and the α phase is increased by reducing the amount of the γ phase and reducing the amount of Sn solidified in the γ phase.

(Melting Casting)

The melting is performed at a temperature of about 100 ° C to about 300 ° C, that is, about 950 ° C to about 1200 ° C, which is higher than the melting point (liquidus temperature) of the alloy of this embodiment. Casting is performed at a temperature about 50 ° C to about 200 ° C higher than the melting point, that is, about 900 ° C to about 1100 ° C. It is cast into a predetermined mold, and is cooled by several cooling methods such as air cooling, slow cooling, and water cooling. In addition, after solidification, various changes occur in the constituent phases.

(Thermal processing)

Examples of the hot working include hot extrusion and hot forging.

Regarding hot extrusion, although it differs depending on the equipment capacity, the hot extrusion is carried out under the condition that the material temperature during the actual hot working, specifically the temperature immediately after passing through the extrusion die (hot working temperature) is 600 to 740 ° C Pressing is better. If the hot working is performed at a temperature exceeding 740 ° C, many β phases are formed during plastic working, and sometimes the β phase may remain and the γ phase may remain more, thereby adversely affecting the constituent phases after cooling. Moreover, even if heat treatment is performed in the next process, the metallographic structure of the hot-worked material is affected. Specifically, compared with the case where hot working is performed at a temperature of 740 ° C. or less, when the hot working is performed at a temperature exceeding 740 ° C., the γ phase becomes larger, or in some cases the β phase remains or thermal processing cracking occurs. The hot working temperature is preferably 670 ° C or lower, and more preferably 645 ° C or lower. When hot extrusion is performed at 645 ° C or lower, the γ phase of the hot-extruded material decreases. When the hot extruded material is subsequently subjected to hot forging and heat treatment to produce a hot forged material or a heat treated material, the amount of the γ phase of the hot forged material or the heat treated material becomes smaller.

When cooling is performed, the average cooling rate in a temperature range of 470 ° C to 380 ° C is set to exceed 2.5 ° C / min and less than 500 ° C / min. The average cooling rate in a temperature range of 470 ° C to 380 ° C is preferably 4 ° C / min or more, and more preferably 8 ° C / min or more. This prevents an increase in the μ phase.

When the hot working temperature is low, the deformation resistance under heat increases. From the viewpoint of deformability, the lower limit of the hot working temperature is preferably 600 ° C or higher, and more preferably 605 ° C or higher. When the extrusion ratio is 50 or less or compared by hot forging For simple shapes, hot working can be performed at 600 ° C or higher. In consideration of the margin, the lower limit of the hot working temperature is preferably 605 ° C. Although it differs depending on the equipment capability, it is preferable that the hot working temperature is as low as possible from the viewpoint of the constituent phase of the metallographic structure.

Considering the measurable measurement position, the hot working temperature is defined as the temperature of the measurable hot working material after about 3 seconds after hot extrusion or hot forging. The metallurgical structure is affected by the temperature just after the large plastic deformation.

A brass alloy containing Pb in an amount of 1 to 4 mass% accounts for most of the copper alloy extruded material. In the case of the brass alloy, in addition to extruding a larger diameter, for example, a diameter exceeding about 38 mm, it is usually It is wound into a coil after hot extrusion. The extruded ingot (small billet) is deprived of heat by the extruder and the temperature is reduced. The extruded material is deprived of heat by contact with the winding device, thereby further reducing the temperature. From the temperature of the ingot that was initially extruded, or from the temperature of the extruded material, a temperature drop of about 50 ° C to 100 ° C occurs at a relatively fast average cooling rate. After that, the wound coil is cooled in a temperature range of 470 ° C to 380 ° C at a relatively slow average cooling rate of about 2 ° C / minute, although the winding coil has a thermal insulation effect, which varies depending on the weight of the coil. When the temperature of the material reaches about 300 ° C, the average cooling rate thereafter becomes further slower, and therefore, water cooling may be performed in consideration of processing. In the case of a brass alloy containing Pb, hot extrusion is performed at about 600 to 800 ° C, but there are a large number of β phases rich in hot workability in the metallurgical structure immediately after extrusion. If the average cold after extrusion However, if the speed is high, a large amount of β phases remain in the cooled metallurgical structure, and the corrosion resistance, ductility, impact characteristics, and high temperature characteristics are deteriorated. In order to avoid such a situation, the cooling is performed at a relatively slow average cooling rate using the heat preservation effect of the extruded coil, etc., thereby changing the β phase to the α phase, thereby becoming a metallographic structure rich in the α phase. As mentioned above, the average cooling rate of the extruded material is relatively fast immediately after extrusion, so it becomes a metallographic structure rich in α phase by slowing down the subsequent cooling. Further, although there is no description of the average cooling rate in Patent Document 1, it is disclosed that in order to reduce the β phase and isolate the β phase, the cooling is slowly performed until the temperature of the extruded material becomes 180 ° C or lower.

As described above, the alloy of this embodiment is produced at a cooling rate that is completely different from the conventional method for producing a brass alloy containing Pb.

(Hot forged)

As a raw material for hot forging, a hot extrusion material is mainly used, but a continuous casting rod may also be used. Compared with hot extrusion, hot forging processes into complex shapes, so the temperature of the raw materials before forging is higher. However, the temperature of the hot forged material to which large plastic working is applied, which is the main part of the forged product, that is, the material temperature about 3 seconds after forging is the same as that of the extruded material, which is 600 ° C to 740 ° C.

In addition, as long as the extrusion temperature at the time of manufacturing the hot extruded rod is reduced, and the metallographic structure has a small amount of γ phase, when hot forging is performed on the hot extruded rod, γ can be obtained even if the hot forging temperature is high. Relatively few hot forged structures.

In addition, by devoting effort to the average cooling rate after forging, a material having various characteristics such as corrosion resistance and machinability can be obtained. That is, the temperature of the forged material at the point of 3 seconds after hot forging is 600 ° C or higher and 740 ° C or lower. In the subsequent cooling process, if in the temperature range of 575 ° C to 510 ° C, especially in the temperature range of 570 ° C to 530 ° C, if the average cooling rate is 0.1 ° C / min or more and 2.5 ° C / min or less, Then the γ phase decreases. In consideration of economy, the lower limit value of the average cooling rate in a temperature range of 575 ° C to 510 ° C is set to 0.1 ° C / min or more. If the average cooling rate exceeds 2.5 ° C / min, the amount of the γ phase decreases. insufficient. The average cooling rate in the temperature range of 575 ° C to 510 ° C is preferably 1.5 ° C / min or less, and more preferably 1 ° C / min or less. Moreover, the average cooling rate in a temperature range of 470 ° C to 380 ° C is set to exceed 2.5 ° C / min and less than 500 ° C / min. The average cooling rate in a temperature range of 470 ° C to 380 ° C is preferably 4 ° C / min or more, and more preferably 8 ° C / min or more. This prevents an increase in the μ phase. Thus, in the temperature range of 575 to 510 ° C, cooling is performed at an average cooling rate of 2.5 ° C / minute or less, preferably 1.5 ° C / minute or less. In the temperature range of 470 to 380 ° C, cooling is performed at an average cooling rate exceeding 2.5 ° C / minute, preferably 4 ° C / minute or more. In this way, the average cooling rate is slowed down in the temperature range of 575 to 510 ° C, and the average cooling rate is reversedly accelerated in the temperature range of 470 to 380 ° C, thereby making a more suitable material.

(Cold working process)

In order to improve the dimensional accuracy or to make the extruded coils straight, it is also possible to cold process the hot extruded material. In detail, cold drawing is performed on a hot extrusion material or a heat-treated material at a processing rate of about 2% to about 20% (preferably about 2% to about 15%, more preferably about 2% to about 10%). Stretch and then correct (compound stretching, correction). Or, for hot extruded materials or heat-treated materials, cold drawing is performed at a processing rate of about 2% to about 20% (preferably about 2% to about 15%, more preferably about 2% to about 10%). . In addition, although the cold working rate is approximately 0%, the linearity of the bar is sometimes improved only by the correction equipment.

(Heat treatment (annealing))

In terms of heat treatment, for example, when processing into a small size that cannot be extruded during hot extrusion, heat treatment is performed after cold drawing or cold drawing as needed, and the material is recrystallized even if it becomes soft. In addition, in the case of a hot-worked material, when a material having almost no processing strain is required or when an appropriate metallographic structure is required, a heat treatment is performed after hot working as necessary.

In brass alloys containing Pb, heat treatment is also performed as needed. In the case of a brass alloy containing Bi in Patent Document 1, heat treatment is performed at a temperature of 350 to 550 ° C. for 1 to 8 hours.

In the case of the alloy of this embodiment, if it is maintained at a temperature of 510 ° C or higher and 575 ° C or lower for 20 minutes or more and 8 hours or less, the corrosion resistance, Improved impact and high temperature characteristics. However, if the heat treatment is performed under the condition that the temperature of the material exceeds 620 ° C., many γ phases or β phases are formed instead, and the α phase becomes coarse. As the heat treatment conditions, the heat treatment temperature is preferably 575 ° C or lower, and more preferably 570 ° C or lower. In the heat treatment at a temperature lower than 510 ° C, the reduction of the γ phase stopped slightly, and the μ phase appeared. Therefore, the temperature of the heat treatment is preferably 510 ° C or higher, and more preferably 530 ° C or higher. The heat treatment time (the time for which the heat treatment temperature is maintained) needs to be maintained at a temperature of 510 ° C or higher and 575 ° C or lower for at least 20 minutes. The holding time helps reduce the γ phase, so the holding time is preferably 30 minutes or more, more preferably 50 minutes or more, and most preferably 80 minutes or more. In terms of economy, the upper limit of the holding time is 480 minutes or less, and preferably 240 minutes or less.

The temperature of the heat treatment is preferably 530 ° C or higher and 570 ° C or lower. Compared with heat treatment at 530 ° C or higher and 570 ° C or lower, in the case of heat treatment at 510 ° C or higher and less than 530 ° C, in order to reduce the γ phase, a heat treatment time of 2 times or 3 times is required.

The value of the heat treatment represented by the following formula is defined by the time (t) (minutes) of the heat treatment and the temperature (T) (° C) of the heat treatment.

(Value of heat treatment) = (T-500) × t

It should be noted that when T is 540 ° C or higher.

The value of the heat treatment is preferably 800 or more, and more preferably 1200 or more.

As described above, by using the high-temperature state after hot extrusion and hot forging, and spending energy on the average cooling rate, it is maintained for a period of more than 20 minutes in a temperature range equivalent to 510 ° C or higher and 575 ° C or lower, that is, During the cooling process, the metallographic structure can be improved by cooling in a temperature range of 575 ° C to 510 ° C at an average cooling rate of 0.1 ° C / minute or more and 2.5 ° C / minute or less. The case where cooling is performed at a temperature of 2.5 ° C./min or less in a temperature range of 575 ° C. to 510 ° C. is substantially the same as the case of holding for 20 minutes in a temperature range of 510 ° C. or more and 575 ° C. or less. In a simple calculation, it is a case where it is heated at a temperature of 510 ° C or higher and 575 ° C or lower for 26 minutes. The average cooling rate is preferably 1.5 ° C / min or less, and more preferably 1 ° C / min or less. In consideration of economy, the lower limit of the average cooling rate is set to 0.1 ° C / min or more.

As another heat treatment method, in the case of a continuous heat treatment furnace in which a hot-extruded material, a hot-forged product, or a material for cold-drawing or a wire is moved in a heat source, if it exceeds 620 ° C, the problem is as described above. However, by temporarily raising the temperature of the material to 575 ° C or higher and 620 ° C or lower, and then maintaining the temperature in a temperature range of 510 ° C or higher and 575 ° C or lower for 20 minutes or more, that is, 510 ° C or higher and The metallographic structure can be improved by cooling at a temperature range of 575 ° C or lower at an average cooling rate of 0.1 ° C / minute or more and 2.5 ° C / minute or less. The average cooling rate in the temperature range of 575 ° C to 510 ° C is preferably 2 ° C / min or less, and more preferably 1.5 ° C / min. Minutes or less, more preferably 1 ° C / minute or less. Of course, it is not limited to a set temperature of 575 ° C or higher. For example, when the maximum temperature reached is 540 ° C, it can also pass at a temperature of 540 ° C to 510 ° C for at least 20 minutes, preferably (T-500) × The value of t is passed under conditions of 800 or more. Increasing the maximum reaching temperature to 550 ° C. or higher to a slightly higher temperature can ensure productivity and obtain a desired metallographic structure.

The advantage of heat treatment is not only to improve corrosion resistance and high temperature characteristics. For hot-worked materials, cold working (such as cold drawing or wire drawing) is performed at a processing rate of 3% to 20%, followed by heat treatment at 510 ° C to 575 ° C, or heat treatment in a continuous annealing furnace equivalent thereto , The tensile strength becomes 550 N / mm ² or more, which exceeds that of the hot-worked material. At the same time, the impact characteristics of heat-treated materials exceed the impact characteristics of hot-worked materials. Specifically, the impact property is sometimes heat-treated material of at least 14J / cm ² or more, 17J / cm ² or more 20J / cm ² or more. Moreover, the intensity index exceeds 690. The principle is considered as follows. When the cold working rate is 3 to 20% and the heating temperature is 510 ° C to 575 ° C, although the two phases, α phase and κ phase, are fully recovered, processing strain remains in the two phases to some extent. In the metallurgical structure, when the hard γ phase decreases, the κ phase increases, the needle-shaped κ phase exists in the α phase, and the α phase increases. As a result, the ductility, impact characteristics, tensile strength, high temperature characteristics, and strength index all exceeded that of hot-worked materials. As a free-cutting copper alloy, among widely used copper alloys, if it is heated to 510 ° C to 575 ° C after cold working at 3 to 20%, it is softened by recrystallization.

Of course, if cold working is performed at a cold working rate of 15% or less after a predetermined heat treatment, the impact characteristics become slightly lower, but a material with a higher strength is obtained, and the strength index exceeds 690.

By adopting this manufacturing process, an alloy having excellent corrosion resistance and excellent impact characteristics, ductility, strength, and machinability is produced.

In these heat treatments, the material is also cooled to normal temperature, but in the cooling process, it is necessary to set the average cooling rate in a temperature range of 470 ° C to 380 ° C to exceed 2.5 ° C / minute and less than 500 ° C / minute. The average cooling rate in a temperature range of 470 ° C to 380 ° C is preferably 4 ° C / min or more. That is, it is necessary to increase the average cooling rate with a boundary around 500 ° C. Generally, the lower the temperature of the cooling performed from the furnace, the slower the average cooling rate.

Regarding the metallurgical structure of the alloy of this embodiment, it is important in the manufacturing process that the average cooling rate in the temperature range of 470 ° C to 380 ° C during the cooling process after heat treatment or after hot working. When the average cooling rate is 2.5 ° C / min or less, the proportion of the μ phase increases. The μ phase is formed mainly around the grain boundaries and phase boundaries. In the harsh environment, μ is inferior to α-phase and κ-phase in corrosion resistance, and therefore causes the selective corrosion and grain boundary corrosion of the μ-phase. In addition, like the γ phase, the μ phase becomes a stress concentration source or a cause of grain boundary slip, and reduces impact characteristics and high-temperature strength. Preferably, in the cooling after hot working, the average cooling in the temperature range of 470 ° C to 380 ° C However, the speed exceeds 2.5 ° C / min, preferably 4 ° C / min or more, more preferably 8 ° C / min or more, and even more preferably 12 ° C / min or more. When the material temperature is quenched from a high temperature of 580 ° C or higher after hot working, for example, if it is cooled at an average cooling rate of 500 ° C / minute or more, many β phases and γ phases may remain. Therefore, the upper limit of the average cooling rate is preferably less than 500 ° C / minute, and more preferably 300 ° C / minute or less.

When the metallographic structure is observed with an electron microscope at a magnification of 2000 or 5000, the average cooling rate of the presence or absence of a μ phase boundary is about 8 ° C./min in a temperature range of 470 ° C. to 380 ° C. In particular, the critical average cooling rate that greatly affects various characteristics is 2.5 ° C./minute or 4 ° C./minute in a temperature range of 470 ° C. to 380 ° C. Of course, the appearance of the μ phase also depends on the composition. The higher the Cu concentration, the higher the Si concentration, the larger the value of the relationship f1 of the metallographic structure, and the lower the value of f2, the faster the formation of the μ phase.

That is, if the average cooling rate in the temperature range of 470 ° C to 380 ° C is slower than 8 ° C / min, the length of the long side of the μ phase precipitated at the grain boundary exceeds about 1 μm, and further progresses as the average cooling rate becomes slower. Grow. When the average cooling rate is about 5 ° C./minute, the length of the long side of the μ phase is changed from about 3 μm to about 10 μm. When the average cooling rate is about 2.5 ° C./min or less, the length of the long side of the μ phase exceeds 15 μm, and in some cases exceeds 25 μm. When the length of the long side of the μ-phase reaches about 10 μm, the μ-phase and the grain boundary can be distinguished in a 1000-fold metal microscope, and observation can be performed. another On the one hand, although the upper limit of the average cooling rate varies depending on the hot working temperature, etc., if the average cooling rate is too fast, the constituent phases formed at high temperatures are directly maintained to normal temperature, and the κ phase increases, which affects the β phase of corrosion resistance and impact characteristics. And γ phase increase. Therefore, the average cooling rate mainly from a temperature range of 580 ° C or higher is important, and it is preferable to perform cooling at an average cooling rate of less than 500 ° C / minute, and more preferably 300 ° C / minute or less.

Currently, brass alloys containing Pb account for most of the extrusion materials of copper alloys. In the case of the brass alloy containing Pb, as described in Patent Document 1, heat treatment is performed at a temperature of 350 to 550 ° C as needed. The lower limit of 350 ° C is the temperature at which recrystallization occurs and the material is approximately softened. At an upper limit of 550 ° C, recrystallization is completed. In addition, there is an energy problem due to an increase in temperature. When the heat treatment is performed at a temperature exceeding 550 ° C, the β phase increases significantly. Therefore, the upper limit is considered to be 550 ° C. As a general manufacturing facility, a split furnace or continuous furnace is used, and it is maintained at a predetermined temperature for 1 to 8 hours. In the case of a split-type furnace, furnace cooling is performed, or after the furnace cooling, air cooling is performed from about 300 ° C. In the case of a continuous furnace, the material is cooled at a relatively slow rate before the temperature of the material is reduced to about 300 ° C. Specifically, in addition to the predetermined temperature maintained, cooling is performed at an average cooling rate of about 0.5 to about 4 ° C / min in a temperature range of 470 ° C to 380 ° C. The cooling is performed at a cooling rate different from that of the method for producing the alloy of this embodiment.

(Low temperature annealing)

In the case of bars and forged products, in order to remove residual stresses and correct the bars, the bars and forged products may be annealed at a temperature lower than the recrystallization temperature. As conditions for this low-temperature annealing, the material temperature is preferably 240 ° C. or higher and 350 ° C. or lower, and the heating time is preferably 10 minutes to 300 minutes. Furthermore, when the temperature (material temperature) of the low-temperature annealing is set to T (° C) and the heating time is set to t (minutes), the temperature is 150. (T-220) × (t) ^1/2 It is preferable to perform low temperature annealing under the conditions of 1200. Here, it is assumed that the heating time t (minutes) is counted (measured) starting from a temperature (T-10) which is 10 ° C lower than the temperature reaching the predetermined temperature T (° C).

When the temperature of the low temperature annealing is lower than 240 ° C, the residual stress is not sufficiently removed, and correction is not performed sufficiently. When the temperature of the low-temperature annealing exceeds 350 ° C., a μ phase is formed around the grain boundary and the phase boundary. If the low-temperature annealing time is less than 10 minutes, the residual stress is not sufficiently removed. When the low-temperature annealing time exceeds 300 minutes, the μ phase increases. As the temperature or time of the low-temperature annealing is increased, the μ phase increases, so that the corrosion resistance, impact characteristics, and high-temperature strength decrease. However, the precipitation of the μ-phase cannot be avoided by performing low-temperature annealing, and how to remove the residual stress and limit the precipitation of the μ-phase to the minimum becomes the key.

The lower limit of the value of (T-220) × (t) ^1/2 is 150, preferably 180 or more, and more preferably 200 or more. The upper limit of the value of (T-220) × (t) ^1/2 is 1200, preferably 1100 or less, and more preferably 1000 or less.

According to this manufacturing method, the free-cutting copper alloys according to the first and second embodiments of the present invention are manufactured.

The hot working process, the heat treatment (annealing) process, and the low temperature annealing process are processes for heating a copper alloy. When the low temperature annealing process is not performed, or the hot working process or the heat treatment (annealing) process is performed after the low temperature annealing process (when the low temperature annealing process does not become the process of heating the copper alloy last), regardless of the presence or absence of cold working The processes performed after the hot working process and the heat treatment (annealing) process become important. When the hot working process is performed after the heat treatment (annealing) process or the heat treatment (annealing) process is not performed after the hot working process (when the hot working process becomes the process of heating the copper alloy last), the hot working process needs to meet the above Heating and cooling conditions. Heat treatment (annealing) when a heat treatment (annealing) process is performed after the hot working process or no heat processing process is performed after the heat treatment (annealing) process (when the heat treatment (annealing) process becomes the process of heating the copper alloy last) The manufacturing process needs to meet the above heating conditions and cooling conditions. For example, when the heat treatment (annealing) process is not performed after the hot forging process, the hot forging process needs to satisfy the heating conditions and cooling conditions of the hot forging described above. When the heat treatment (annealing) process is performed after the hot forging process, the heat treatment (annealing) process needs to satisfy the heating conditions and cooling conditions of the above heat treatment (annealing). In this case, the hot forging process does not necessarily have to satisfy the heating conditions and cooling conditions of the hot forging described above.

In the low temperature annealing process, the material temperature is above 240 ° C and below 350 ° C. This temperature is related to whether or not the μ phase is formed, and has nothing to do with the temperature range (575 ~ 510 ° C) where the γ phase is reduced. In this way, the material temperature in the low temperature annealing process has nothing to do with the increase or decrease of the γ phase. Therefore, when the low temperature annealing process is performed after the hot working process or the heat treatment (annealing) process (when the low temperature annealing process becomes the process of heating the copper alloy last), together with the conditions of the low temperature annealing process, the temperature before the low temperature annealing process The heating conditions and cooling conditions of the manufacturing process (the process of heating the copper alloy immediately before the low temperature annealing process) become important. The low temperature annealing process and the processes before the low temperature annealing process need to meet the above heating conditions and cooling conditions. In detail, in the process before the low temperature annealing process, the heating conditions and cooling conditions in the hot working process, the heat treatment (annealing) process, and the process performed after the process also become important, and it is necessary to satisfy the above heating conditions and cooling condition. When a hot working process or a heat treatment (annealing) process is performed after the low temperature annealing process, as described above, in the hot working process, the heat treatment (annealing) process, and the process performed after the process becomes important, it is necessary to meet the above heating conditions and cooling condition. Furthermore, a hot working process or a heat treatment (annealing) process may be performed before or after the low temperature annealing process.

The free-cutting alloy according to the first and second embodiments of the present invention configured as described above has the alloy composition, the composition relational expression, the metallographic structure, and the structural relational expression defined as described above, so the corrosion resistance under harsh environments Chong Excellent impact properties and high temperature strength. Moreover, even if the content of Pb is small, excellent machinability can be obtained.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical requirement of the invention.

[Example]

The results of confirmation experiments performed to confirm the effects of the present invention are shown below. In addition, the following examples are for explaining the effect of the present invention, and the constituent elements, processes, and conditions described in the examples do not limit the technical scope of the present invention.

(Example 1)

<Practical experiments>

A prototype test of copper alloy was carried out using a low-frequency furnace and a semi-continuous casting machine used in actual operation. Table 2 shows the alloy composition. In addition, since actual operating equipment was used, impurities were also measured in the alloys shown in Table 2. The manufacturing process was performed under the conditions shown in Tables 5 to 10.

(Process No.A1 ~ A12, AH1 ~ AH9)

A small billet with a diameter of 240 mm was manufactured using a low-frequency furnace and a semi-continuous casting machine in actual operation. The raw materials are used according to the actual operator. The billet was cut to a length of 800 mm and heated. It was hot-extruded to have a round rod shape with a diameter of 25.6 mm, and was wound into a coil (extruded material). Then, by The insulation of the coil and the adjustment of the fan, in the temperature range of 575 ° C to 510 ° C and the temperature range of 470 ° C to 380 ° C, cool the extruded material at an average cooling rate of 20 ° C / min. Cooling is also performed in a temperature range of 380 ° C or lower at an average cooling rate of about 20 ° C / minute. The temperature was measured using a radiation thermometer around the last stage of hot extrusion, and the temperature of the extruded material was measured about 3 seconds after the extruder was extruded. In addition, a DS-06DF radiation thermometer manufactured by Daido Steel Co., Ltd. was used.

It was confirmed that the average value of the temperature of the extruded material was ± 5 ° C of the temperature shown in Table 5 (within the temperature shown in Table 5) -5 ° C to (temperature shown in Table 5) + 5 ° C. ).

In process Nos. AH2, A9, and AH9, the extrusion temperatures were set to 760 ° C, 680 ° C, and 580 ° C, respectively. In processes other than Process Nos. AH2, A9, and AH9, the extrusion temperature was set to 640 ° C. In process No. AH9 with an extrusion temperature of 580 ° C, the three materials prepared were not extruded to the end and were abandoned.

After extrusion, only correction was performed in process Nos. AH1 and AH2.

In process Nos. A10 and A11, the extruded material having a diameter of 25.6 mm was heat-treated. Next, in process Nos. A10 and A11, cold drawing was performed at a cold working ratio of about 5% and about 9%, respectively, and then corrected to make the diameters 25mm and 24.4mm (composite stretching and correction after heat treatment were performed). ).

In process No. A12, cold drawing was performed with a cold working ratio of about 9%, and then correction was performed so that the diameter became 24.4 mm (composite drawing, correction). This was followed by heat treatment.

In processes other than the above, cold drawing with a cold working ratio of about 5% is performed, and then correction is performed so that the diameter becomes 25 mm (composite drawing, correction). This was followed by heat treatment.

As shown in Table 5, regarding the heat treatment conditions, the temperature of the heat treatment was changed to 500 ° C to 635 ° C, and the holding time was also changed to 5 minutes to 180 minutes.

In process Nos. A1 to A6, A9 to A12, AH3, AH4, and AH6, a split furnace is used to change the average cooling rate in the temperature range of 575 ° C to 510 ° C or 470 ° C to 380 ° C in the cooling process. The average cooling rate in the temperature region.

In process Nos. A7, A8, AH5, AH7, and AH8, a continuous annealing furnace is used to heat at a high temperature for a short time, and then the average cooling rate in the temperature range of 575 ° C to 510 ° C or 470 ° C is changed. The average cooling rate in the temperature range to 380 ° C.

In the table below, "○" indicates that the composite stretching and correction were performed before the heat treatment, and "-" indicates that it was not performed.

(Process No.B1 ~ B3, BH1 ~ BH3)

The material (rod) with a diameter of 25 mm obtained in Process No. A10 was cut to a length of 3 m. The bars are then arranged on a template to correct Aim Low temperature annealing was performed. The low-temperature annealing conditions at this time were used as the conditions shown in Table 7.

The value of the conditional expression in the table is the value of the following expression.

(Conditional expression) = (T-220) × (t) ^1/2

T: temperature (material temperature) (° C), t: heating time (minutes)

As a result, only the linearity of the process No. BH1 was poor.

(Process No.C0, C1, C2, CH1, CH2)

An ingot (small billet) with a diameter of 240 mm was manufactured by using a low-frequency furnace and a semi-continuous casting machine in actual operation. The raw materials are used according to the actual operator. The billet was cut to a length of 500 mm and heated. Then, a hot extruded material was used as a round rod-shaped extruded material having a diameter of 50 mm. The extruded material was extruded in a straight bar shape at an extrusion station. The temperature was measured using a radiation thermometer around the last stage of the extrusion, and the temperature of the extruded material was measured about 3 seconds after the point of extrusion with the extruder. It was confirmed that the average value of the temperature of the extruded material was within ± 5 ° C of the temperature shown in Table 8 (within the temperature shown in Table 8) -5 ° C to (temperature shown in Table 8) + 5 ° C. ). In addition, the average cooling rate of 575 ° C to 510 ° C and the average cooling rate of 470 ° C to 380 ° C after extrusion were 15 ° C / minute (extruded material). In the process described later, the extruded material (round bar) obtained in the process Nos. C0 and CH2 was used as a raw material for forging. In process Nos. C1, C2, and CH1, heating was performed at 560 ° C for 60 minutes, and then the average cooling rate of 470 ° C to 380 ° C was changed.

(Process No.D1 ~ D8, DH1 ~ DH5)

A round rod having a diameter of 50 mm obtained in Process No. C0 was cut to a length of 180 mm. The round bar was placed in the horizontal direction, and the thickness was 16 mm by using a hot forging press with a capacity of 150 tons. The temperature was measured using a radiation thermometer after about 3 seconds after the hot forging was performed to a predetermined thickness. It was confirmed that the hot forging temperature (hot working temperature) was within the range of the temperature ± 5 ° C shown in Table 9 (within the temperature shown in Table 9) -5 ° C ~ (the temperature shown in Table 9) + 5 ° C ).

In process Nos. D6 and DH5, the average cooling rate in a temperature range of 575 ° C to 510 ° C was changed after hot forging and implemented. In processes other than Process No. D6 and DH5, cooling is performed at an average cooling rate of 20 ° C./minute after hot forging.

In process Nos. DH1, D6, and DH5, the sample preparation operation was completed by cooling after hot forging. In processes other than Process Nos. DH1, D6, and DH5, the following heat treatment was performed after hot forging.

In process Nos. D1 to D4 and DH2, heat treatment is performed in a split furnace, and the temperature of the heat treatment is changed, the average cooling rate in a temperature range of 575 ° C to 510 ° C, and the average value in a temperature range of 470 ° C to 380 ° C. The cooling rate is implemented. In the process No. D5, DH3, and DH4, the heating was performed at 600 ° C for 3 minutes or 2 minutes in a continuous furnace, and the average cooling rate was changed.

In addition, the temperature of heat treatment is the highest reaching temperature of the material. The holding time is a holding time in a temperature range from the highest reaching temperature to (the highest reaching temperature -10 ° C).

<Laboratory experiment>

A prototype test of a copper alloy was performed using laboratory equipment. Tables 3 and 4 show alloy compositions. Moreover, the remainder is Zn and unavoidable impurities. The copper alloys of the composition shown in Table 2 were also used in laboratory experiments. The manufacturing process was performed under the conditions shown in Tables 11 and 12.

(Process No.E1 ~ E3, EH1)

In the laboratory, the raw materials were melted at a prescribed composition ratio. The molten metal was cast into a metal mold having a diameter of 100 mm and a length of 180 mm to prepare a small billet. This small billet was heated and extruded into a round bar with a diameter of 25 mm in process Nos. E1 and EH1 and corrected. In process Nos. E2 and E3, a round rod with a diameter of 40 mm was extruded and corrected. In Table 11, "○" indicates that the correction was performed.

The temperature was measured using a radiation thermometer immediately after the extrusion tester was stopped. The result corresponds to the temperature of the extruded material after about 3 seconds from the time of extrusion with an extruder.

In the process Nos. EH1 and E2, the production operation using extrusion as a sample is completed. The extruded material obtained in the process No. E2 is used as a raw material for hot forging in a process described later.

In addition, a continuous casting rod with a diameter of 40 mm was produced by continuous casting. It is used as a hot forging material in a process described later.

In process Nos. E1 and E3, heat treatment (annealing) was performed under the conditions shown in Table 11 after extrusion.

(Process No.F1 ~ F5, FH1, FH2)

The round bar having a diameter of 40 mm obtained in Process No. E2 was cut to a length of 180 mm. A round rod of process No. E2 or the aforementioned continuous casting rod was placed in the horizontal direction, and was forged using a hot forging press with a capacity of 150 tons to a thickness of 15 mm. About 3 seconds passed after the hot forging to a predetermined thickness, the temperature was measured using a radiation thermometer. It was confirmed that the hot forging temperature (hot working temperature) was within the range of the temperature ± 5 ° C shown in Table 12 (within the temperature shown in Table 12) -5 ° C to the temperature shown in Table 12 + 5 ° C. ).

The average cooling rate in a temperature range of 575 ° C to 510 ° C and the average cooling rate in a temperature range of 470 ° C to 380 ° C were set to 20 ° C / minute and 18 ° C / minute, respectively. In the process No. FH1, the round bar obtained in the process No. E2 was subjected to hot forging, and the cooling operation after the hot forging was used as a sample to end.

In the process Nos. F1, F2, and FH2, the round bar obtained in the process No. E2 was subjected to hot forging, and heat treatment was performed after the hot forging. Heat treatment (annealing) was performed while changing heating conditions, the average cooling rate in a temperature range of 575 ° C to 510 ° C, and the average cooling rate in a temperature range of 470 ° C to 380 ° C.

In process Nos. F3 and F4, hot forging was performed using a continuous casting rod as a forging material. After hot forging, heat treatment (annealing) was performed by changing heating conditions and average cooling rate.

The above test materials were evaluated for metallographic structure observation, corrosion resistance (dezincification corrosion test / immersion test), and machinability by the following procedures.

(Observation of Metallographic Structure)

The metallographic structure was observed by the following method, and the area ratios (%) of the α phase, κ phase, β phase, γ phase, and μ phase were measured by image analysis. The α 'phase, β' phase, and γ 'phase are included in the α phase, β phase, and γ phase, respectively.

The bars and forged products of each test material were cut parallel to the longitudinal direction or parallel to the flow direction of the metallographic structure. Then, the surface was polished (mirror face polishing) and etched with a mixed solution of hydrogen peroxide and ammonia. During the etching, an aqueous solution obtained by mixing 3 mL of 3 vol% hydrogen peroxide water and 14 vol% of ammonia water 22 mL was used. At a room temperature of about 15 ° C to about 25 ° C, the polished surface of the metal is immersed in the aqueous solution for about 2 seconds to about 5 seconds.

Using a metal microscope, the metallographic structure was observed mainly at a magnification of 500 times, and the metallographic structure was observed at a magnification of 1,000 times depending on the state of the metallographic structure. In the photomicrographs of 5 fields of view, each phase (α-phase, κ-phase, β-phase, γ-phase, μ-phase) was manually coated with an image processing software "PhotoshopCC". Then, the image processing software "WinROOF2013" was used for binarization to obtain the area ratio of each phase. Specifically, for each phase, an average value of area ratios of 5 fields of view was obtained, and the average value was set as Comparison rate. The total area ratio of all constituent phases is 100%.

The lengths of the long sides of the γ phase and the μ phase were measured by the following methods. The maximum length of the long side of the γ phase was measured in one field of view using 500 times or 1000 times the metal micrograph. This operation is performed in any of the five fields of view, the average value of the maximum length of the long side of the γ phase is calculated, and the length of the long side of the γ phase is set. Similarly, depending on the size of the μ phase, using 500 or 1000 times metal photomicrographs or 2000 or 5000 times secondary electron image (electron micrograph), μ was measured in one field of view. The maximum length of the long side of the phase. This operation is performed in any of the five fields of view, and the average value of the maximum lengths of the long sides of the μ phase is calculated and set as the length of the long sides of the μ phase.

Specifically, evaluation was performed using a photo printed with a size of about 70 mm × about 90 mm. In the case of 500x magnification, the size of the observation field of view is 276 μm × 220 μm.

When phase identification is difficult, the phase is specified at a magnification of 500 or 2000 times by the FE-SEM-EBSP (Electron Back Scattering Diffracton Pattern) method.

Moreover, in the example of changing the average cooling rate, in order to confirm the presence or absence of the μ phase mainly precipitated at the grain boundaries, JSMOL-7000F manufactured by JEOL Ltd. was used at an acceleration voltage of 15 kV and a current value (set value 15) Take a secondary electron image and confirm it at a magnification of 2000 or 5000 Metallographic organization. When the μ phase can be confirmed with a secondary electron image of 2000 or 5000 times, but the μ phase cannot be confirmed with a metal micrograph of 500 or 1000 times, the area ratio is not calculated. That is, the μ phase observed by the secondary electron image at 2000 or 5000 times but not confirmed in the metal micrograph at 500 or 1000 times is not included in the area ratio of the μ phase. This is because the μ phase that cannot be confirmed with a metal microscope mainly has a length of about 5 μm or less and a width of about 0.3 μm or less, and therefore has a small effect on the area ratio.

The length of the μ phase is measured in any of the five fields of view, and the average value of the longest length in the five fields of view is the length of the long side of the μ phase as described above. The composition of the μ phase was confirmed by the attached EDS. Furthermore, when the μ phase cannot be confirmed at 500 or 1000 times, but the length of the long side of the μ phase is measured at a higher magnification, the area ratio of the μ phase is 0% in the measurement results in the table. However, the length of the long side of the μ phase is still recorded.

(Observation of μ phase)

About the μ phase, the presence of the μ phase can be confirmed if the μ phase is cooled in a temperature range of 470 ° C. to 380 ° C. at an average cooling rate of 8 ° C./minute or less than 15 ° C./minute after hot extrusion or heat treatment. FIG. 1 shows an example of a secondary electron image of Test No. T05 (Alloy No. S01 / Process No. A3). Precipitation of the μ phase (white-gray slender phase) was confirmed at the grain boundaries of the α-phase.

(Needle-like κ phase present in α phase)

The width of the needle-like κ phase (κ1 phase) existing in the α phase is about 0.05 μm It is about 0.5 μm in length and has a slender, linear, needle-like shape. If the width is 0.1 μm or more, its existence can be confirmed even by using a metal microscope.

FIG. 2 shows a metal photomicrograph of Test No. T53 (Alloy No. S02 / Process No. A1) as a representative metal photomicrograph. FIG. 3 shows an electron micrograph of Test No. T53 (Alloy No. S02 / Process No. A1) as a representative electron micrograph of a needle-like κ phase existing in the α phase. Moreover, the observation positions in FIGS. 2 and 3 are different. In the copper alloy, it may be confused with the twin crystals existing in the α phase, but in the case of the kappa phase existing in the α phase, the width of the kappa phase itself is narrow, and the twin crystal system is two groups, so they can be distinguished. In the metal micrograph of FIG. 2, the phase of the slender straight needle-like pattern can be observed in the α phase. The secondary electron image (electron micrograph) in FIG. 3 clearly confirmed that the pattern existing in the α phase was the κ phase. The κ phase has a thickness of about 0.1 to about 0.2 μm.

The amount (number) of acicular κ phases in the α phase was determined with a metal microscope. In the determination of the metal constituent phase (metallographic observation), photomicrographs of 5 fields of view taken at 500 or 1000 times magnification were used. The number of needle-like kappa phases was measured in an enlarged field of view having a length of about 70 mm and a width of about 90 mm, and an average value of 5 fields of view was obtained. When the average of the number of acicular κ phases in 5 fields of view is 5 or more and less than 49, it is judged that the acicular κ phase has the acicular κ phase, and is recorded as "Δ". When the average of the number of acicular κ phases in the five fields of view exceeds 50, it is judged that there are many acicular κ phases, and it is recorded as "○". When the needle When the average of the number of κ-phases in the 5 fields of view is 4 or less, it is determined that there is almost no needle-shaped κ-phases, and it is described as “×”. The number of acicular κ1 phases that cannot be confirmed with photos is not included.

(Sn amount, P amount contained in κ phase)

The amount of Sn and P contained in the κ phase were measured using an X-ray microanalyzer. The measurement was carried out using "JXA-8200" manufactured by JEOL Ltd., under the conditions of an acceleration voltage of 20 kV and a current value of 3.0 × 10 ^-8 A.

Test No.T03 (Alloy No.S01 / Process No.A1), Test No.T25 (Alloy No.S01 / Process No.BH3), Test No.T229 (Alloy No.S20 / Process No.EH1), Test Table 13 to Table 16 show the results of quantitative analysis of the concentrations of Sn, Cu, Si, and P in each phase using X-ray microanalyzer No. T230 (Alloy No. S20 / Process No. E1).

The μ phase was measured using an EDS attached to JSM-7000F, and a portion with a large short side length in the field of view was measured.

The following findings were obtained from the above measurement results.

1) The concentration distributed in each phase is slightly different depending on the alloy composition.

2) The distribution of Sn in the κ phase is about 1.4 times that of the α phase.

3) The Sn concentration in the γ phase is about 10 to about 15 times the Sn concentration in the α phase.

4) Compared with the Si concentration of the α phase, the Si concentrations of the κ phase, γ phase, and μ phase are about 1.5 times, about 2.2 times, and about 2.7 times, respectively.

5) The Cu concentration of μ phase is higher than that of α phase, κ phase, γ phase, and μ phase.

6) If the proportion of the γ phase is increased, the Sn concentration of the κ phase is necessarily reduced.

7) The distribution of P in the κ phase is approximately twice that of the α phase.

8) The P concentration in the γ phase is about 3 times the P concentration in the α phase, and the P concentration in the μ phase is about 4 times the P concentration in the α phase.

9) Even with the same composition, if the ratio of the γ phase is reduced, the Sn concentration of the α phase is increased by about 1.7 times from 0.13 mass% to 0.22 mass% (Alloy No. S20). Similarly, the Sn concentration of the kappa phase increased by about 1.7 times from 0.18 mass% to 0.31 mass%. When the proportion of the γ phase decreases, the Sn concentration of the α phase increases from 0.13 mass% to 0.18 mass% by 0.05 mass%, and the Sn concentration of the κ phase increases from 0.22 mass% to 0.31 mass% by 0.09 mass%. The increase amount of Sn in the κ phase exceeds the increase amount of Sn in the α phase.

(Mechanical characteristics)

(tensile strength)

Each test material was processed into No. 10 test piece of JIS Z 2241, and the tensile strength was measured. If the tensile strength of the hot forging or hot extrusion material material is 530N / mm ² or more (preferably 550N / mm ² or more), it is easy to cut copper in the alloy is also the highest level, it is possible to use in various fields Thinner and lighter components.

Furthermore, the roughness of the finished surface of the tensile test piece affects the elongation and tensile strength. degree. Therefore, a tensile test piece was produced so as to satisfy the following conditions.

(Conditions of Roughness of Finished Surface of Tensile Test Strip)

In a cross-sectional curve of 4 mm per reference length at any position between the punctuation points of the tensile test piece, the difference between the maximum value and the minimum value of the Z axis is 2 μm or less. The cross-sectional curve refers to a curve obtained by applying a low-pass filter having a cutoff value λ s to a cross-sectional curve.

(High temperature creep)

A flanged test piece with a diameter of 10 mm in accordance with JIS Z 2271 was produced from each test piece. The creep strain after 100 hours at 150 ° C was measured in a state where a load corresponding to a guaranteed stress of 0.2% of room temperature was applied to the test piece. A load equivalent to 0.2% of plastic deformation is applied at the elongation between the punctuation points at normal temperature. If the test piece is held at 150 ° C for 100 hours under the load, the creep strain is 0.4% or less. good. If the creep strain is 0.3% or less, it is the highest level among copper alloys. For example, it can be used as a highly reliable material in valves that can be used at high temperatures and in automotive components close to the engine room.

(Impact characteristics)

In the impact test, a U-shaped notch test piece (notch depth 2mm, notch bottom radius 1mm) according to JIS Z 2242 was selected from extruded bars, forged materials and their alternative materials, casting materials, and continuous casting bars. . A Charpy impact test was performed with an impact blade having a radius of 2 mm, and the impact value was measured.

In addition, the impact value when using a V-notch test piece and a U-notch test piece The relationship is roughly as follows.

(V-notch impact value) = 0.8 × (U-shaped notch impact value) -3

(Machinability)

As the evaluation of the machinability, the cutting test using a lathe was evaluated as follows.

Hot-extruded rods with a diameter of 50mm, 40mm, or 25.6mm, and cold-drawn materials with a diameter of 25mm (24.4mm) were cut to produce test materials with a diameter of 18mm. The forged material was cut to produce a test material with a diameter of 14.5 mm. A point nose straight tool, especially a tungsten carbide tool without chip breaker, is installed on the lathe. Using this lathe, under dry conditions, under the conditions of a rake angle of -6 degrees, a cutting edge radius of 0.4mm, a cutting speed of 150m / min, a cutting depth of 1.0mm, and a feed speed of 0.11mm / rev, the diameter is 18mm or The test material with a diameter of 14.5 mm was cut on the circumference.

A signal from an dynamometer (manufactured by Miho Electric Manufacturing Co., Ltd., AST-type tool dynamometer AST-TL1003) including three parts mounted on the tool is converted into an electrical voltage signal and recorded in a recorder. These signals are then converted into cutting resistance (N). Therefore, the machinability of the alloy was evaluated by measuring the main component force that showed the highest value in cutting resistance, particularly during cutting.

At the same time, chips were selected and the machinability was evaluated based on the chip shape. The biggest problem in practical cutting is that the chips are wrapped in tools or The chip volume is large. Therefore, a case where only chips having a chip shape of 1 roll or less was generated was evaluated as “○” (good). A case where chips having a chip shape exceeding 1 roll and 3 rolls were evaluated was "Δ" (fair). A case where chips having a chip shape exceeding three rolls were evaluated was evaluated as “×” (poor). In this way, evaluation was performed in three stages.

Cutting resistance also depends on the strength of the material, such as shear stress, tensile strength and 0.2% guaranteed stress. The higher the strength, the higher the cutting resistance of the material. If the cutting resistance is about 10% to about 20% higher than the cutting resistance of a free-cutting brass rod containing 1 to 4% of Pb, it is sufficiently tolerated in practical use. In the present embodiment, the cutting resistance was evaluated with a boundary (boundary value) of 130N. Specifically, if the cutting resistance is less than 130N, it is evaluated that the machinability is excellent (evaluation: ○). When the cutting resistance is 130N or more and less than 150N, the machinability is evaluated as "OK (Δ)". When the cutting resistance was 150 N or more, it was evaluated as "defective (×)". In addition, 58 mass% Cu-42mass% Zn alloy was produced by process No. F1 to prepare a sample and evaluated. As a result, the cutting resistance was 185N.

As a comprehensive evaluation of the machinability, the chip shape was good (evaluation: ○) and the cutting resistance was low (evaluation: ○) as being excellent in machinability (excellent). When one of the chip shape and the cutting resistance is Δ or acceptable, the cutting condition is evaluated to be good. When one of the chip shape and the cutting resistance was Δ or acceptable, and the other was × or poor, it was evaluated as poor cutting.

(Hot working test)

A test material was produced by cutting a rod having a diameter of 50 mm, a diameter of 40 mm, a diameter of 25.6 mm, or a diameter of 25.0 mm into a diameter of 15 mm, and cutting it into a length of 25 mm. The test material was held at 740 ° C or 635 ° C for 20 minutes. Next, the test material was placed vertically, and an Amsler tester equipped with an electric furnace with a thermal compression capacity of 10 tons was used to perform high-temperature compression at a strain rate of 0.02 / second and a processing rate of 80%, so that the thickness became 5 mm.

Regarding the evaluation of hot workability, when a crack of an opening of 0.2 mm or more was observed using a 10-fold magnifying glass, it was judged that cracking occurred. A case where cracking did not occur under both conditions of 740 ° C and 635 ° C was evaluated as "Good" (good). A case where a crack occurred at 740 ° C but no crack occurred at 635 ° C was evaluated as "Δ" (fair). A case where no crack occurred at 740 ° C but a crack occurred at 635 ° C was evaluated as "▲" (fair). A case where cracking occurred under both conditions of 740 ° C and 635 ° C was evaluated as "poor".

When cracking does not occur under both conditions of 740 ° C and 635 ° C, regarding the hot extrusion and hot forging in actual use, as far as the implementation is concerned, even if the temperature of some materials drops, Although the material is instant but has contact and the temperature of the material decreases, as long as it is implemented at an appropriate temperature, there is no problem in practical use. When cracking occurs at any of 740 ° C and 635 ° C, although it is limited in practical use, as long as it is managed in a narrower temperature range, it is determined that hot working can be performed. When cracking occurs at both temperatures of 740 ° C and 635 ° C, it is judged as practical use There is a problem.

(Dezincification corrosion test 1, 2)

When the test material is an extruded material, the test material is implanted into the phenolic resin material such that the surface of the exposed sample of the test material is perpendicular to the extrusion direction. When the test material is a casting material (casting rod), the test material is implanted into the phenol resin material so that the surface of the exposed sample of the test material is perpendicular to the longitudinal direction of the casting material. When the test material is a forged material, the phenolic resin material is implanted so that the surface of the exposed sample of the test material is perpendicular to the forging flow direction.

The surface of the sample was ground with a gold-steel sandpaper up to No. 1200, followed by ultrasonic cleaning in pure water and drying with a blower. Then, each sample was immersed in the prepared immersion liquid.

After the test, the sample was re-implanted into the phenol resin material so that the exposed surface was perpendicular to the extrusion direction, the long-side direction, or the forging flow direction. Next, the sample was cut so that the cross section of the corroded part was obtained as the longest cut part. The sample was then ground.

Using a metal microscope, the depth of corrosion was observed in 10 microscope fields (arbitrary 10 fields) at a magnification of 500 times. The deepest corrosion point is recorded as the maximum dezincification corrosion depth.

In the dezincification corrosion test 1, the following test liquid 1 was prepared as an immersion liquid, and the above operation was performed. In the dezincification corrosion test 2, the following test liquid 2 was prepared as an immersion liquid, and the above operation was performed.

The test solution 1 is a solution for assuming a severely corrosive environment with a low pH as a disinfectant as an oxidant, and further performing an accelerated test under the corrosive environment. If this solution is used, it is estimated that the accelerated test will be about 75 to 100 times that in the severe corrosive environment. When the maximum corrosion depth is 70 μm or less, the corrosion resistance is good. When excellent corrosion resistance is required, it is estimated that the maximum corrosion depth is preferably 50 μm or less, and more preferably 30 μm or less.

The test solution 2 is a solution for assuming a harsh corrosive environment with a high chloride ion concentration and a low pH, and further performing an accelerated test under the corrosive environment. If this solution is used, it is estimated that the accelerated test will be approximately 30 to 50 times in this severe corrosive environment. When the maximum corrosion depth is 40 μm or less, the corrosion resistance is good. When excellent corrosion resistance is required, it is estimated that the maximum corrosion depth is preferably 30 μm or less, and more preferably 20 μm or less. In this example, evaluation was performed based on these estimated values.

In the dezincification corrosion test 1, as the test liquid 1, hypochlorous acid water (concentration: 30 ppm, pH = 6.8, water temperature: 40 ° C) was used. The test liquid 1 was adjusted by the following method. Commercially available sodium hypochlorite (NaClO) was added to 40 L of distilled water, and adjusted so that the residual chlorine concentration by the iodine titration method became 30 mg / L. Residual chlorine decomposes and decreases with time. Therefore, the residual chlorine concentration is often measured by voltammetry, and the amount of sodium hypochlorite input is electronically controlled by an electromagnetic pump. In order to lower the pH to 6.8, the carbon dioxide was adjusted while the flow rate was adjusted. The temperature of the water was adjusted by a temperature controller to 40 ° C. In this way, the residual chlorine is concentrated The temperature, pH, and water temperature were kept constant, and the sample was held in the test solution 1 for two months. Then, the sample was taken out from the aqueous solution, and the maximum value of the dezincification corrosion depth (maximum dezincification corrosion depth) was measured.

In the dezincification corrosion test 2, as the test liquid 2, test water having a composition shown in Table 17 was used. The test solution 2 was adjusted by putting a commercially available drug into distilled water. It is assumed that a highly corrosive water pipe is charged with 80 mg / L of chloride ion, 40 mg / L of sulfate ion, and 30 mg / L of nitrate ion. The alkalinity and hardness were adjusted to 30mg / L and 60mg / L, respectively, based on the general Japanese water pipe. In order to lower the pH to 6.3, the carbon dioxide was injected while adjusting the flow rate of carbon dioxide, and oxygen was often injected to saturate the dissolved oxygen concentration. The water temperature was the same as room temperature, and it was performed at 25 ° C. In this way, the pH and water temperature were kept constant, and the dissolved oxygen concentration was set to a saturated state, and the sample was held in the test solution 2 for three months. Then, the sample was taken out from the aqueous solution, and the maximum value (maximum dezincification corrosion depth) of the dezincification corrosion depth was measured.

(Dezincification corrosion test 3: ISO6509 dezincification corrosion test)

This test is used in many countries as a method of dezincification corrosion test, and it is also specified in JIS H 3250 in the JIS standard.

The test material was implanted into the phenol resin material in the same manner as in the dezincification corrosion test 1 and 2. For example, the exposed sample surface is implanted into the phenol resin material such that the surface of the exposed sample is perpendicular to the extrusion direction of the extruded material. The surface of the sample was polished with gold-steel sandpaper up to No. 1200, and then ultrasonically washed in pure water and dried.

Each sample was immersed in an aqueous solution (12.7 g / L) of 1.0% copper chloride dihydrate and a salt (CuCl ₂ .2H ₂ O), and maintained at a temperature of 75 ° C. for 24 hours. After that, the sample was taken out of the aqueous solution.

The specimen was re-implanted into the phenolic resin material such that the exposed surface was perpendicular to the direction of extrusion, the direction of the long side, or the direction of the flow of the forging. Next, the sample was cut so that the cross section of the corroded part was obtained as the longest cut part. The sample was then ground.

Using a metal microscope, the depth of corrosion was observed in 10 fields of view of the microscope at a magnification of 100 to 500 times. The deepest corrosion point is recorded as the maximum dezincification corrosion depth.

In addition, when the test of ISO 6509 is performed, if the maximum corrosion depth is 200 μm or less, it becomes a level that has no problem with corrosion resistance in practical use. In particular, when excellent corrosion resistance is required, the maximum corrosion depth is preferably 100 μm or less, and more preferably 50 μm or less.

In this test, a case where the maximum corrosion depth exceeds 200 μm is evaluated as “poor”. A case where the maximum corrosion depth exceeds 50 μm and 200 μm or less is evaluated as “fair”. The maximum corrosion depth is 50 μm or less The situation was strictly evaluated as "○" (good). In the present embodiment, strict evaluation criteria are adopted in order to assume a severe corrosive environment, and only a case where the evaluation is "○" is regarded as a good corrosion resistance.

(Abrasion test)

The abrasion resistance was evaluated by two tests, an Amsler type abrasion test under lubricating conditions and a ball-on-disk friction abrasion test under dry conditions. The samples used were alloys made in process Nos. C0, C1, CH1, E2, and E3.

An Amsler type abrasion test was performed by the following method. Each sample was cut at room temperature so that the diameter became 32 mm, and an upper test piece was produced. In addition, a lower test piece (surface hardness HV184) with a diameter of 42 mm manufactured by Vostian Iron Stainless Steel (SUS304 of JIS G 4303) was prepared. A load of 490 N was applied to bring the upper and lower test pieces into contact. Oil droplets and oil baths use silicone oil. In a state where the upper test piece and the lower test piece are brought into contact with a load, the upper test piece and the lower test piece have a rotation speed (rotation speed) of 188 rpm and a lower test piece rotation speed (rotation speed) of 209 rpm. Slice rotation. The slip speed was set to 0.2 m / sec using the peripheral speed difference between the upper and lower test pieces. As the diameter and the rotation speed (rotation speed) of the upper test piece and the lower test piece are different, the test piece is worn. The upper test piece and the lower test piece were rotated until the number of rotations of the lower test piece reached 250,000 times.

After the test, the weight change of the upper test piece was measured, and the abrasion resistance was evaluated by the following criteria. The weight of the upper test piece will be generated by abrasion When the amount of reduction was 0.25 g or less, it was evaluated as "excellent". The case where the weight reduction of the upper test piece exceeded 0.25 g and 0.5 g or less was evaluated as "Good" (good). The case where the weight loss of the upper test piece was more than 0.5 g and 1.0 g or less was evaluated as “Δ” (fair). The case where the weight reduction of the upper test piece exceeded 1.0 g was evaluated as "poor". The abrasion resistance was evaluated through these four stages. In addition, in the lower test piece, when abrasion loss of 0.025 g or more was present, it was evaluated as “×”.

In addition, the abrasion loss (amount of weight reduction due to abrasion) of free-cutting brass containing 59Cu-3Pb-38Zn Pb under the same test conditions was 12 g.

A ball-disk friction abrasion test was performed by the following method. The surface of the test piece was polished with a sandpaper of roughness # 2000. A steel ball with a diameter of 10 mm made by Vostian Iron Stainless Steel (SUS304 of JIS G 4303) was pushed onto the test piece under the following conditions and slid.

(condition)

Room temperature, non-lubricated, load: 49N, sliding diameter: 10mm in diameter, sliding speed: 0.1m / sec, sliding distance: 120m.

After the test, the weight change of the test piece was measured, and the abrasion resistance was evaluated by the following criteria. The case where the weight reduction of the test piece by abrasion was 4 mg or less was evaluated as "excellent". A case where the weight of the test piece was reduced to more than 4 mg and 8 mg or less was evaluated as "Good" (good). A case where the weight of the test piece was reduced to more than 8 mg and less than 20 mg was evaluated as “fair”. Evaluation of a case where the weight of the test piece is reduced by more than 20 mg "X" (poor). The abrasion resistance was evaluated through these four stages.

In addition, the abrasion loss of free-cutting brass containing Pb of 59Cu-3Pb-38Zn under the same test conditions was 80 mg.

The evaluation results are shown in Tables 18 to 47.

Test Nos. T01 to T98 and T101 to T150 are the results of actual experiments. Test Nos. T201 to T258 and T301 to T308 are results corresponding to examples in laboratory experiments. Test Nos. T501 to T546 are results corresponding to comparative examples in laboratory experiments.

"* 1" described in the process number in the table indicates the following matters.

* 1) Evaluation of hot workability was performed using EH1 material.

In addition, regarding the test described as "EH1, E2" or "E1, E3" in the process number, the abrasion test was implemented using the sample produced in process number E2 or E3. The samples prepared in Process No. EH1 or E1 were used to perform all tests except corrosion tests, mechanical properties, and other investigations, as well as investigation of metallographic structure.

The above experimental results are summarized as follows.

1) It can be confirmed that by satisfying the composition of this embodiment, and satisfying the compositional relations f1, f2, the requirements of the metallurgical structure and the organization relational expressions f3, f4, f5, and f6, a good content is obtained by containing a small amount of Pb Machinability and hot extruded materials and hot forged materials with good hot workability and excellent corrosion resistance in harsh environments, with high strength, good impact characteristics, abrasion resistance and high temperature characteristics ( For example, alloy No. S01, S02, and 13, process No. A1, C1, D1, E1, F1, F3).

2) It can be confirmed that the inclusion of Sb and As further improves the corrosion resistance under severe conditions (alloy Nos. S41 to S45).

3) It was confirmed that by including Bi, the cutting resistance was further reduced (Alloy No. S43).

4) It can be confirmed that the κ phase contains 0.08 mass% or more of Sn and 0.07 mass% or more of P, thereby improving corrosion resistance, cutting performance, and strength (for example, alloy Nos. S01, S02, and S13).

5) It can be confirmed that due to the presence of the slender needle-like κ phase, that is, the κ1 phase, in the α phase, the strength is increased, the strength index is improved, the machinability is well maintained, and the corrosion resistance is improved (for example, alloy Nos. S01, S02, 13) .

6) When the Cu content is small, the γ phase increases and the machinability is good, but the corrosion resistance, impact characteristics, and high-temperature characteristics deteriorate. Conversely, when the Cu content is large, the machinability is deteriorated. In addition, the impact characteristics are also deteriorated (Alloy Nos. S119, S120, S122, etc.).

7) If the Sn content is greater than 0.28 mass%, the area ratio of the γ phase will be greater than 1.5%, and the machinability is good, but the corrosion resistance, impact characteristics, and high temperature characteristics are deteriorated (Alloy S111). On the other hand, if the Sn content is less than 0.07 mass%, the depth of dezincification corrosion in a severe environment is large (Alloy Nos. S114 to S117). When the Sn content is 0.1 mass% or more, the characteristics are further improved (alloys S26, S27, and S28).

8) If the P content is large, the impact characteristics are deteriorated. The cutting resistance is slightly higher. On the other hand, if the P content is small, the depth of dezincification corrosion in a severe environment is large (Alloy Nos. S109, S113, and S115).

9) It is possible to confirm that Avoidable impurities will not greatly affect various characteristics (Alloy Nos. S01, S02, S03). It is considered that if the composition is outside the composition range or the boundary value of the present embodiment, but exceeds the limit of unavoidable impurities, an intermetallic compound of Fe and Si or an intermetallic compound of Fe and P is formed. As a result, the effective Si concentration and P concentration are reduced, the corrosion resistance is deteriorated, and the interaction with the formation of the intermetallic compound reduces the cutting performance slightly (Alloy Nos. S124, S125).

10) If the value of the composition relational expression f1 is low, even if Cu, Si, Sn, and P are in the composition range, the depth of dezincification corrosion in a severe environment is large (Alloy Nos. S110, S101, and S126).

11) When the value of the composition relational expression f1 is low, the γ phase is increased and the machinability is good, but the corrosion resistance, impact characteristics, and high temperature characteristics are deteriorated. When the value of the composition relational expression f1 is high, the κ phase is increased, and the machinability, hot workability, and impact characteristics are deteriorated (Alloy Nos. S109, S104, S125, and S121).

12) If the value of the composition relationship f2 is low, the machinability is good, but the hot workability, corrosion resistance, impact characteristics, and high temperature characteristics are deteriorated. When the value of the composition relational expression f2 is high, the hot workability is deteriorated, and a problem occurs in hot extrusion. In addition, the machinability deteriorated (Alloy Nos. S104, S105, S103, S118, S119, S120, S123).

13) In the metallographic structure, if the proportion of the γ phase is greater than 1.5% or the length of the long side of the γ phase is greater than 40 μm, the machinability is good, but the corrosion resistance, impact characteristics, and high temperature characteristics are deteriorated. In particular, if the γ phase increases, Selective corrosion of γ phase occurred in the dezincification corrosion test under the environment (alloy Nos. S101, S110, S126). When the ratio of the γ phase is 0.8% or less and the length of the long side of the γ phase is 30 μm or less, the corrosion resistance, impact characteristics, and high-temperature characteristics become good (Alloy Nos. S01 and S11).

When the area ratio of the μ phase is more than 2% or the length of the long side of the μ phase exceeds 25 μm, the corrosion resistance, impact characteristics, and high-temperature characteristics are deteriorated. In the dezincification corrosion test under severe environment, grain boundary corrosion or μ-phase selective corrosion occurs (Alloy No. S01, Process No. AH4, BH3, DH2). When the proportion of the μ phase is 1% or less and the length of the long side of the μ phase is 15 μm or less, the corrosion resistance, impact characteristics, and high-temperature characteristics become good (alloys S01 and S11).

When the area ratio of the κ phase is more than 65%, the machinability and impact characteristics are deteriorated. On the other hand, if the area ratio of the κ phase is less than 25%, the machinability is poor (Alloy Nos. S122 and S105).

14) If the structural relationship f5 = (γ) + (μ) exceeds 2.5% or f3 = (α) + (κ) is less than 97%, the corrosion resistance, impact characteristics, and high-temperature characteristics deteriorate. When the structural relational expression f5 is 1.5% or less, the corrosion resistance, impact characteristics, and high temperature characteristics are improved (Alloy No. S1, Process No. AH2, A1, Alloy No. S103, S23).

If the structural relationship formula f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) is greater than 70 or less than 27, the machinability is poor (Alloy Nos. S105 and 122, Process Nos. E1 and F1). When f6 is 32 or more and 62 or less, the machinability is further improved (alloys S01 and S11).

When the area ratio of the γ phase exceeds 1.5%, irrespective of the value of the structural relationship f6, the cutting resistance is reduced and the shape of the chip is also good (alloys S103, S112, etc.).

15) If the amount of Sn contained in the κ phase is less than 0.08 mass%, the depth of dezincification corrosion in a severe environment will increase, and corrosion of the κ phase will occur. In addition, the cutting resistance was also slightly higher, and there were also cases where the chip had poor segmentability (Alloy Nos. S114 to S117). When the amount of Sn contained in the κ phase is more than 0.11 mass%, the corrosion resistance and the machinability become good (alloys S26, S27, and S28).

16) If the amount of P contained in the κ phase is less than 0.07 mass%, the depth of dezincification corrosion in a severe environment will increase, and corrosion of the κ phase will occur. (Alloy Nos. S113, S115, S116).

17) If the area ratio of the γ phase is 1.5% or less, the Sn and P concentrations contained in the κ phase are higher than the amounts of Sn and P contained in the alloy. Compared with the amount of Sn and P contained in the alloy, the smaller the area ratio of the γ phase, the higher the Sn concentration and the P concentration contained in the κ phase. On the contrary, if the area ratio of the γ phase is large, the concentration of Sn contained in the κ phase is lower than the amount of Sn contained in the alloy. In particular, if the area ratio of the γ phase is approximately 10%, the Sn concentration contained in the κ phase is approximately half of the amount of Sn contained in the alloy (alloys S01, S02, S03, S14, S101, S108). For example, in alloy S20, if the area ratio of the γ phase is reduced from 5.9% to 0.5%, the Sn concentration of the α phase increases from 0.13 mass% to 0.18 mass% by 0.05 mass%, and the Sn concentration of the κ phase increases from 0.22 mass. % To 0.31mass% increased by 0.09mass%. Thus, the increase amount of Sn in the κ phase exceeds the increase amount of Sn in the α phase. If the γ phase decreases, the increase in the distribution of Sn in the κ phase and the presence of more needle-like κ phases in the α phase will increase the cutting resistance by 7N, but maintain good machinability and enhance the corrosion resistance of the κ phase. Dezincification corrosion depth is reduced to approximately 1/4, impact value is approximately 1/2, high temperature creep is reduced to 1/3, tensile strength is increased by 43N / mm ² , and strength index is increased by 77.

18) As long as the requirements for all components and metallographic structure are met, the tensile strength is 530 N / mm ² or more, the load is equivalent to 0.2% of the guaranteed stress at room temperature and the creep is maintained at 50 ° C for 100 hours. The strain is 0.3% or less (alloy Nos. S103, S112, etc.).

19) As long as the requirements for the entire composition and the requirements for the metallographic structure are satisfied, the Charpy impact test value of the U-shaped notch is 14 J / cm ² or more. The Charpy impact test value of the U-shaped notch in a hot-extruded material or a forged material that has not been cold-worked is 17 J / cm ² or more. Moreover, the strength index also exceeded 670 (alloy Nos. S01, S02, S13, S14, etc.).

The amount of Si was about 2.95%, and the needle-like κ phase began to exist in the α phase. The amount of Si was about 3.1%, and the needle-like κ phase increased significantly. The relationship f2 affects the amount of acicular κ phase (alloy Nos. S31, S32, S101, S107, S108, etc.).

When the amount of the acicular κ phase increases, the machinability, tensile strength, and high-temperature characteristics become good. It is presumed to be related to the enhancement of the α phase and chip splitting properties (alloy Nos. S02, S13, S23, S31, S32, S101, S107, S108, etc.).

The test method of ISO6509 contains more than 3% β phase or about 5% The above γ phase, or alloys containing no P or 0.01% are unacceptable (evaluation: △, ×), but alloys containing 3 to 5% γ phase and approximately 3% of the mu phase are acceptable (evaluation: ○). The corrosive environment used in this embodiment is based on those who assume a harsh environment (Alloy Nos. S14, S106, S107, S112, S120).

In terms of wear resistance, an alloy having many needle-like kappa phases, containing about 0.10% to 0.25% of Sn, and containing about 0.1 to about 1.0% of the γ phase, is excellent both under lubrication and without lubrication ( Alloy No. S14, S18, etc.).

20) Evaluation of materials using mass production equipment and materials made in the laboratory yielded approximately the same results (Alloy No. S01, S02, Process No. C1, C2, E1, F1).

21) About manufacturing conditions: For hot-extruded materials, extruded / stretched materials, and hot-forged products, hold for more than 20 minutes in a temperature range of 510 ° C and above 575 ° C or in a continuous furnace at 510 ° C and above 575 ° C When the temperature is cooled at an average cooling rate of 2.5 ° C / min or less, and at an average cooling rate of 2.5 ° C / min or more in a temperature range of 480 ° C to 370 ° C, the γ phase is greatly reduced and there is almost no μ Materials with excellent corrosion resistance, high temperature characteristics, impact characteristics, and mechanical strength.

In the process of heat-treating hot-worked materials and cold-worked materials, if the temperature of the heat treatment is low, the reduction of the γ phase is small, and the corrosion resistance, impact characteristics, and high-temperature characteristics are poor. If the temperature of the heat treatment is high, the crystal grains of the α phase become Coarse, less reduction of γ phase, so poor corrosion resistance, impact characteristics, poor machinability, and low tensile strength (alloy No. S01, S02, S03, process No. A1, AH5, AH6). When the heat treatment temperature is 520 ° C., if the holding time is short, the decrease in the γ phase is small. If the relationship between the heat treatment time (t) and the heat treatment temperature (T) is expressed in the formula, it is (T-500) × t (where T is 540 ° C or higher, it is 540). When the formula is 800 or more, the γ phase decreases more (process Nos. A5, A6, D1, D4, and F1).

In the cooling after heat treatment, if the average cooling rate in the temperature range of 470 ° C to 380 ° C is slow, there are μ phases, and the corrosion resistance, impact characteristics, and high temperature characteristics are poor, and the tensile strength is also low (Alloy Nos. S01, S02 , S03, process No. A1 ~ A4, AH8, DH2, DH3).

After the heat treatment, the proportion of the γ phase of the hot-extruded material is low, and the corrosion resistance, impact characteristics, tensile strength, and high-temperature characteristics are good. (Alloy No.S01, S02, S03, Process No.A1, A9)

As a heat treatment method, temporarily increase the temperature to 575 ° C to 620 ° C, and slow down the average cooling rate in the temperature region of 575 ° C to 510 ° C during the cooling process, thereby obtaining good corrosion resistance, impact characteristics, and high temperature characteristics. Improvements in characteristics were also confirmed in the continuous heat treatment method (alloy Nos. S01, S02, S03, process Nos. A1, A7, A8, D5).

In the heat treatment, if the temperature is increased to 635 ° C, the length of the long side of the γ phase becomes longer, the corrosion resistance is poor, and the strength is reduced. Even at 500 ° C The heating and holding time, the reduction of the γ phase is also small (alloy No. S01, S02, S03, process No. AH5, AH6).

In the cooling after hot forging, by controlling the average cooling rate in the temperature range of 575 ° C to 510 ° C to 1.5 ° C / min, a forged product having a small proportion of the γ phase after hot forging is obtained. (Alloy No. S01, S02, S03, Process No. D6).

Even if a continuous casting rod is used as a hot forging raw material, good various characteristics (alloy Nos. S01, S02, S03, and process Nos. F3, F4) are obtained similarly to the extruded material.

With proper heat treatment and appropriate cooling conditions after hot forging, the amount of Sn and P contained in the κ phase (alloy No. S01, S02, S03, process No. A1, AH1, C0, C1, D6 ).

After subjecting the extruded material to cold processing at a processing rate of about 5% and about 9%, a predetermined heat treatment is performed, and the corrosion resistance, impact characteristics, high temperature characteristics, and tensile strength of the extruded material are improved compared to hot extruded materials. The tensile strength is increased by about 70 N / mm ² , about 90 N / mm ² , and the strength index is also increased by about 90 (alloy No. S01, S02, S03, process No. AH1, A1, A12). By performing heat treatment (annealing) of the cold-worked material at a high temperature of 540 ° C, an alloy can be obtained which maintains good machinability, has excellent corrosion resistance, high strength, and has high temperature characteristics and impact characteristics.

When the heat-treated material is processed at a cold working rate of 5%, the tensile strength is increased by about 90 N / mm ² compared with the extruded material, and the impact value is the same or more, and the corrosion resistance and high temperature characteristics are also improved. When the cold working ratio is set to about 9%, the tensile strength is increased by about 140 N / mm ² , but the impact value is slightly reduced (alloy Nos. S01, S02, and S03, process Nos. AH1, A10, and A11).

When a predetermined heat treatment is performed on the hot-worked material, it is confirmed that the amount of Sn contained in the κ phase increases and the γ phase decreases significantly, but good machinability is ensured (Alloy Nos. S01 and S02, Process Nos. AH1, A1 , D7, C0, C1, EH1, E1, FH1, F1).

If an appropriate heat treatment is performed, acicular κ phases (alloy Nos. S01, S02, and S03, process Nos. AH1, A1, D7, C0, C1, EH1, E1, FH1, and F1) will be present in the α phase. It is presumed that due to the presence of the needle-like κ phase in the α phase, the tensile strength and abrasion resistance are improved, and the machinability is also good, which compensates for the substantial decrease in the γ phase.

When low temperature annealing is performed after cold working or hot working, it can be confirmed that heating is performed at a temperature of 240 ° C or higher and 350 ° C or lower from 10 minutes to 300 minutes, and the heating temperature is set to T ° C and the heating time is set to t minutes. If 150 (T-220) × (t) ^1/2 If the heat treatment is performed under the conditions of 1200, a cold-worked material and a hot-worked material (alloy No. S01, process No. B1 to B3) having excellent corrosion resistance in a harsh environment, good impact characteristics, and high temperature characteristics can be obtained.

In the samples in which alloys No. S01 to S03 were subjected to the process No. AH9, the deformation resistance was high and they could not be squeezed out to the end, so the subsequent evaluation was suspended.

In the process No. BH1, inadequate correction and low temperature annealing are not appropriate, thereby causing quality problems.

According to the above, as in the alloy of the present embodiment, the alloy system of the present embodiment has a hot workability (hot extrusion) in which the content of each additional element, the composition relationship formula, the metallographic structure, and the structure relationship formula are within appropriate ranges. , Hot forging) is excellent, and corrosion resistance and machinability are also good. In addition, in order to obtain excellent characteristics in the alloy of this embodiment, it can be achieved by setting the manufacturing conditions during hot extrusion and hot forging, and the conditions during heat treatment to appropriate ranges.

(Example 2)

As for the alloy of the comparative example of this embodiment, a copper alloy Cu-Zn-Si alloy casting (test No. T601 / alloy No. S201) which had been used for 8 years in a severe water environment was obtained. Furthermore, there is no detailed information on the water quality of the environment used. The composition and metallographic analysis of Test No. T601 were performed in the same manner as in Example 1. Moreover, the corrosion state of the cross section was observed using a metal microscope. Specifically, the sample was implanted into the phenol resin material so that the exposed surface was perpendicular to the long side direction. Next, the sample was cut so that the cross section of the corroded part was obtained as the longest cut part. The sample was then ground. The cross section was observed using a metal microscope. The maximum corrosion depth was measured.

Next, a similar alloy casting was produced under the same composition and production conditions as those of Test No. T601 (Test No. T602 / Alloy No. S202). A similar alloy casting (Test No. T602) was described in Example 1. Composition, analysis of metallographic structure, evaluation (measurement) of mechanical properties, etc., and dezincification corrosion tests 1 to 3. Furthermore, the corrosion state based on the actual water environment of test No. T601 and the corrosion state based on the accelerated test of dezincification corrosion tests 1 to 3 of test No. T602 were compared to verify the accelerated test of the dezincification corrosion tests 1 to 3 Effectiveness.

In addition, the evaluation results (corrosion state) of the dezincification corrosion test 1 of the alloy (Test No. T28 / Alloy No. S01 / Process No. C2) of this embodiment described in Example 1 and the corrosion of Test No. T601 The state and the evaluation result (corrosion state) of the dezincification corrosion test 1 of Test No. T602 were compared, and the corrosion resistance of Test No. T28 was examined.

Test No. T602 was produced by the following method.

The raw materials were melted so as to have a composition almost the same as that of Test No. T601 (Alloy No. S201), and were cast into a mold having an inner diameter of φ40 mm at a casting temperature of 1000 ° C to produce a casting. After that, the casting is cooled at a temperature range of 575 ° C to 510 ° C at an average cooling rate of about 20 ° C / min, and then at a temperature range of 470 ° C to 380 ° C at an average cooling rate of about 15 ° C / min. . Based on the above, a sample of Test No. T602 was produced.

The composition, the analysis method of the metallographic structure, the measurement methods of the mechanical properties, and the methods of the dezincification corrosion tests 1 to 3 are as described in Example 1.

The obtained results are shown in Tables 48 to 50 and FIG. 4.

In a copper alloy casting (test No. T601) that has been used for 8 years in a harsh water environment, at least the contents of Sn and P are outside the range of this embodiment.

FIG. 4 (a) shows a metal micrograph of a cross section of Test No. T601.

In Test No. T601, after 8 years of use in a harsh water environment, the maximum corrosion depth of the corrosion caused by the use environment was 138 μm.

Dezincification corrosion (a depth of about 100 μm from the surface on the average) occurred on the surface of the corroded part regardless of the α phase and the κ phase.

In the corroded portion where the α phase and the κ phase are corroded, there is a non-defective α phase as it goes toward the inside.

The corrosion depth of the α phase and κ phase has unevenness rather than constant. It is generally from the boundary to the inside. Corrosion occurs only in the γ phase (from the boundary portion where the α and κ phases are corroded to a depth of about 40 μm: locally generated. Corrosion on the γ phase only).

FIG. 4 (b) shows a metal micrograph of a cross section after the dezincification corrosion test 1 of Test No. T602.

The maximum corrosion depth is 146 μm.

Dezincification corrosion (a depth of about 100 μm from the surface on the average) occurred on the surface of the corroded part regardless of the α phase and the κ phase.

Among them, there is a non-defective α phase as it goes toward the inside.

The corrosion depth of the α phase and κ phase is uneven and not constant, and generally from the boundary portion toward the inside. Corrosion occurs only in the γ phase (from the boundary portion where the α phase and κ phase are corroded, only the locally generated γ phase corrosion length (Approximately 45 μm).

It is understood that the corrosion caused by the awful water environment in FIG. 4 (a) during 8 years is substantially the same as the corrosion generated by the dezincification corrosion test 1 in FIG. 4 (b). In addition, since the amounts of Sn and P do not satisfy the range of the present embodiment, both the α phase and the κ phase are corroded at the portion where water is in contact with the test solution, and the γ phase is selectively corroded at the ends of the corroded portion. The concentrations of Sn and P in the κ phase are low.

The maximum corrosion depth of test No. T601 is slightly shallower than the maximum corrosion depth of dezincification corrosion test 1 of test No. T602. However, the maximum corrosion depth of Test No. T601 is slightly deeper than the maximum corrosion depth of Dezincification Corrosion Test 2 of Test No. T602. The degree of corrosion caused by the actual water environment is affected by the water quality, but the results of the dezincification corrosion test 1 and 2 and the corrosion result by the actual water environment are roughly consistent in both the corrosion form and the corrosion depth. Therefore, it was found that the conditions of the dezincification corrosion tests 1 and 2 are valid, and in the dezincification corrosion tests 1 and 2, evaluation results that are substantially the same as the corrosion results caused by the actual water environment were obtained.

The acceleration rate of the corrosion test methods 1 and 2 is approximately the same as the corrosion caused by the actual harsh water environment. It is considered that this case is based on the corrosion test methods 1 and 2 assuming severe environments.

The result of the dezincification corrosion test 3 (ISO6509 dezincification corrosion test) of Test No. T602 was "Good" (good). Therefore, the results of the dezincification corrosion test 3 do not agree with the corrosion results caused by the actual water environment.

The test time for dezincification corrosion test 1 is two months, about 75 ~ 100 Times the accelerated test. The test time of the dezincification corrosion test 2 is three months, which is about 30 to 50 times the accelerated test. On the other hand, the test time of the dezincification corrosion test 3 (ISO6509 dezincification corrosion test) is 24 hours, which is an accelerated test of about 1000 times or more.

For example, the dezincification corrosion tests 1 and 2 are considered to be performed for a long period of two to three months by using a test liquid closer to the actual water environment, thereby obtaining an evaluation approximately the same as the corrosion results caused by the actual water environment. result.

In particular, in the corrosion results of test No. T601 caused by a severe water environment in 8 years and the corrosion results of dezincification corrosion tests 1 and 2 of test No. T602, the corrosion of the γ phase to the α phase and κ phase of the surface Corroded together. However, in the corrosion results of the dezincification corrosion test 3 (ISO6509 dezincification corrosion test), the γ phase was hardly corroded. Therefore, it is considered that in the dezincification corrosion test 3 (ISO6509 dezincification corrosion test), it is not possible to properly evaluate the corrosion of the γ phase with the corrosion of the α phase and the κ phase on the surface and the corrosion caused by the actual water environment The results were inconsistent.

FIG. 4 (c) shows a metal micrograph of a cross section after the dezincification corrosion test 1 of Test No. T28 (Alloy No. S01 / Process No. C2).

Near the surface, about 40% of the γ and κ phases exposed on the surface are corroded. However, the remaining κ phase and α phase were flawless (uncorroded). The maximum corrosion depth is also about 25 μm. Furthermore, as it turned toward the inside, selective corrosion of a γ phase or a μ phase occurred at a depth of about 20 μm. It is considered that the length of the long side of the γ phase or the μ phase is one of the great factors determining the depth of corrosion.

Compared with test Nos. T601 and T602 of FIGS. 4 (a) and (b), it was found in test No. T28 of this embodiment of FIG. 4 (c) that the corrosion of the α phase and the κ phase near the surface was greatly obtained. inhibition. It is presumed that this delays the progress of corrosion. According to the observation results of the corrosion morphology, it is considered that the corrosion resistance of the κ phase is improved by including Sn in the κ phase as a main factor that greatly suppresses the corrosion of the α phase and the κ phase near the surface.

[Industrial availability]

The free-cutting copper alloy of the present invention is excellent in hot workability (hot-extrudability and hot-forgeability), and has excellent corrosion resistance and machinability. Therefore, the free-cutting copper alloy of the present invention is suitable for electrical / automotive / mechanical / industrial piping components such as faucets, valves, joints, and other appliances, valves, joints, and valves used in daily drinking water for humans and animals. In appliances and components in contact with liquid.

Specifically, it can be suitably applied to faucet fittings, mixed faucet fittings, drainage fittings, faucet bodies, hot water heater components, water heater (EcoCute) components, hose accessories, and water jets that are used for drinking water, drainage, and industrial water. Devices, water meters, hydrants, fire hydrants, hose connections, water supply and drainage cocks, pumps, headers, pressure reducing valves, valve seats, gate valves, valves, stems, unions, Flange, corporation cock, faucet valve, ball valve, various valves, piping joint materials, etc., such as elbow, socket, cheese, elbow, connector, adapter, T Tube, joints (joint) and other name users.

In addition, it can be suitably applied to a solenoid valve used as an automobile component, Control valves, various valves, radiator components, oil cooler components, cylinders, piping joints for mechanical components, valves, valves, stems, heat exchanger components, water supply and drainage cocks, cylinders, pumps, as industrial piping components Pipe fittings, valves, valves, stems, etc.

Claims (14)

A free-cutting copper alloy characterized by containing 75.0 mass% or more and 78.5 mass% or less of Cu, 2.95 mass% or more and 3.55 mass% or less of Si, 0.07 mass% or more and 0.28 mass% or less of Sn, 0.06 mass % Or more and 0.14mass% or less P and 0.022mass% or more and 0.25mass% or less Pb, and the remaining part includes Zn and unavoidable impurities, when the Cu content is set to [Cu] mass%, Si content When [Si] mass%, Sn content is [Sn] mass%, P content is [P] mass%, and Pb content is [Pb] mass%, the relationship is as follows: 76.2

f1 = [Cu] + 0.8 × [Si] -8.5 × [Sn] + [P] + 0.5 × [Pb]

80.3, 61.5

f2 = [Cu] -4.3 × [Si] -0.7 × [Sn]-[P] + 0.5 × [Pb]

63.3, and, among the constituent phases of the metallographic structure, when the area ratio of the α phase is (α)%, the area ratio of the β phase is (β)%, and the area ratio of the γ phase is (γ )%, When the area ratio of the κ phase is (κ)% and the area ratio of the μ phase is (μ)%, there is the following relationship: 25

(κ)

65, 0

(γ)

1.5, 0

(β)

0.2, 0

(μ)

2.0, 97.0

f3 = (α) + (κ), 99.4

f4 = (α) + (κ) + (γ) + (μ), 0

f5 = (γ) + (μ)

2.5, 27

f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ)

70, and the length of the long side of the γ phase is 40 μm or less, the length of the long side of the μ phase is 25 μm or less, and the κ phase exists in the α phase. The free-cutting copper alloy according to claim 1, further comprising Sb selected from 0.02 mass% or more and 0.08 mass% or less, As, 0.02 mass% or more and 0.30 mass% selected from 0.02 mass% or more and 0.08 mass% or less One or more of the following Bi. A free-cutting copper alloy characterized by containing 75.5mass% or more and 78.0mass% or less of Cu, 3.1mass% or more and 3.4mass% or less of Si, 0.10mass% or more and 0.27mass% or less of Sn, 0.06mass % And more than 0.13mass% and less P and 0.024mass% and more than 0.24mass% and less Pb, and the remaining part includes Zn and unavoidable impurities, when the Cu content is set to [Cu] mass%, Si content When [Si] mass%, Sn content is [Sn] mass%, P content is [P] mass%, and Pb content is [Pb] mass%, the relationship is as follows: 76.6

f1 = [Cu] + 0.8 × [Si] -8.5 × [Sn] + [P] + 0.5 × [Pb]

79.6, 61.7

f2 = [Cu] -4.3 × [Si] -0.7 × [Sn]-[P] + 0.5 × [Pb]

63.2, and among the constituent phases of the metallographic structure, when the area ratio of the α phase is (α)%, the area ratio of the β phase is (β)%, and the area ratio of the γ phase is (γ )%, When the area ratio of the κ phase is (κ)% and the area ratio of the μ phase is (μ)%, there is the following relationship: 30

(κ)

56, 0

(γ)

0.8, (β) = 0, 0

(μ)

1.0, 98.0

f3 = (α) + (κ), 99.6

f4 = (α) + (κ) + (γ) + (μ), 0

f5 = (γ) + (μ)

1.5, 32

f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ)

62, and the length of the long side of the γ phase is 30 μm or less, the length of the long side of the μ phase is 15 μm or less, and the κ phase exists in the α phase. The free-cutting copper alloy according to claim 3, which further contains Sb selected from more than 0.02 mass% and 0.07 mass% or less, As, more than 0.02 mass% and 0.07 mass% or less, As, 0.02 mass% and more than 0.20 mass% One or more of the following Bi. The free-cutting copper alloy according to any one of claims 1 to 4, wherein the total amount of Fe, Mn, Co, and Cr as the inevitable impurities is less than 0.08 mass%. The free-cutting copper alloy according to any one of claims 1 to 4, wherein the amount of Sn contained in the κ phase is 0.08 mass% or more and 0.45 mass% or less, and the amount of P contained in the κ phase 0.07mass% or more and 0.24mass% or less. The free-cutting copper alloy according to claim 5, wherein the amount of Sn contained in the κ phase is 0.08 mass% or more and 0.45 mass% or less, and the amount of P contained in the κ phase is 0.07 mass% or more and Below 0.24mass%. The requested item 1 to 4 of any one of the free cutting copper alloy, wherein the Charpy impact test value exceeds 14J / cm ² and less than 50J / cm ^2, a tensile strength of 530N / mm ² or more, and Under a load equivalent to 0.2% guaranteed stress at room temperature, the creep strain after holding at 150 ° C for 100 hours is 0.4% or less. The free-cutting copper alloy as described in claim 5, wherein the Charpy impact test value exceeds 14J / cm ² and less than 50J / cm ² , the tensile strength is 530N / mm ² or more, and the equivalent Under the condition that 0.2% of the temperature guarantees the stress load, the creep strain after holding at 150 ° C for 100 hours is 0.4% or less. The free-cutting copper alloy according to any one of claims 1 to 4, which is used in water pipe appliances, industrial piping members, appliances in contact with liquids, automobile components, or electrical product components. The free-cutting copper alloy according to claim 5, which is used in appliances for plumbing, industrial piping members, appliances in contact with liquids, automotive components or electrical product components. A method for manufacturing a free-cutting copper alloy, which is a method for manufacturing a free-cutting copper alloy according to any one of claims 1 to 11, characterized by having either one of a cold working process and a hot working process Or both; and, the annealing process performed after the cold working process or the hot working process; in the annealing process, the temperature is maintained at 510 ° C or more and 575 ° C or less for 20 minutes to 8 hours, or at 575 ° C to 510 The temperature range of ℃ is cooled at an average cooling rate of 0.1 ° C / min or more and 2.5 ° C / min or less, and then, in the temperature range of 470 ° C to 380 ° C, at an average cooling rate of more than 2.5 ° C / min and less than 500 ° C / min Allow to cool. A method for manufacturing a free-cutting copper alloy, which is the method for manufacturing a free-cutting copper alloy according to any one of claims 1 to 11, characterized in that it includes a hot working process, and the material temperature during hot working is 600 ° C or more and 740 ° C or less, when hot extrusion is performed as the aforementioned hot working, during cooling, the average cooling rate in the temperature range of 470 ° C to 380 ° C exceeds 2.5 ° C / min and less than 500 ° C / min Cooling is performed, and when hot forging is performed as the aforementioned hot working, during the cooling process, it is cooled at an average cooling rate of 0.1 ° C / min to 2.5 ° C / min in the temperature range of 575 ° C to 510 ° C, at 470 ° C The temperature range up to 380 ° C is cooled at an average cooling rate of more than 2.5 ° C / min and less than 500 ° C / min. A method for manufacturing a free-cutting copper alloy, which is a method for manufacturing a free-cutting copper alloy according to any one of claims 1 to 11, characterized by having either one of a cold working process and a hot working process Or both; and, the low temperature annealing process performed after the cold working process or the hot working process; in the low temperature annealing process, when the material temperature is set to a range of 240 ° C or more and 350 ° C or less, the heating time is set to In the range of 10 minutes or more and 300 minutes or less, when the material temperature is T ° C and the heating time is t minutes, it is 150

(T-220) × (t) ^1/2

1200 conditions.